AJG Arthur J Gallagher and Company

As filed with the Securities and Exchange Commission on February 18, 2025.

Registration No. 333-______

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-8

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

ARTHUR J. GALLAGHER & CO.

(Exact name of registrant as specified in its charter)

Arthur J. Gallagher & Co.

2850 W. Golf Road

Rolling Meadows, Il 60008

(Address of Principal Executive Offices, Zip Code)

Arthur J. Gallagher & Co. Employees’ 401(k) Savings and Thrift Plan

Arthur J. Gallagher & Co. Supplemental Savings and Thrift Plan

Stand Alone Restricted Stock Unit Inducement Awards*

(Full Title of the Plans)

*See Explanatory Note on Following Page

Walter D. Bay, Esq.

General Counsel and Secretary

2850 W. Golf Road

Rolling Meadows, Il 60008

(630) 773-3800

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Sean Feller

Gibson, Dunn & Crutcher LLP

2029 Century Park East, Suite 4000

Los Angeles, CA 90067-3026

(310) 552-8500

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☐

EXPLANATORY NOTE

This Registration Statement on Form S-8 is filed by Arthur J. Gallagher & Co. (the “Company”) and the Arthur J. Gallagher & Co. Employees’ 401(k) Savings and Thrift Plan (the “401(k) Plan”) to register (i) an additional 1,000,000 shares of common stock, par value $1.00 per share (“Common Stock”), that may be offered and sold to accounts of eligible employees of the Company under the 401(k) Plan; (ii) an additional 100,000 shares of Common Stock, that may be offered and sold under the Arthur J. Gallagher & Co. Supplemental Savings and Thrift Plan (the “Supplemental Plan”); and (iii) 1,200,000 shares of common stock, par value $1.00 per share (“Common Stock”), that may be offered and issued in connection with the grant of employment inducement awards pursuant to NYSE Listed Company Manual Rule 303A.08 in the form of stand alone restricted stock unit awards to certain award recipients (“RSU Inducement Awards”). On December 7, 2024, the Company entered into a Stock Purchase Agreement, by and among the Company, The AssuredPartners Group LP, a Delaware limited partnership, and Dolphin Topco, Inc., a Delaware corporation (the “Acquired Entity”), pursuant to which the Company will acquire all of the issued and outstanding stock of the Acquired Entity (the “Transaction”). In connection with the Transaction, the Company will issue the RSU Inducement Awards as a material inducement for employees of the Acquired Entity to become employees of the Company.

PART I

INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

The documents containing the information specified in Part I of Form S-8 have been or may be delivered to individuals as inducement for employment and to participants in the 401(k) Plan and the Supplemental Plan as specified by Rule 428(b)(1) promulgated by the Securities and Exchange Commission (the “SEC”) under the Securities Act of 1933, as amended (the “Securities Act”). Such documents are not being filed by the Company with the SEC but constitute (along with the documents incorporated by reference into this registration statement pursuant to Item 3 of Part II hereof) a prospectus that meets the requirements of Section 10(a) of the Securities Act.

PART II

INFORMATION REQUIRED IN REGISTRATION STATEMENT

Item 3. Incorporation of Documents by Reference.

The SEC’s rules allow the Company to incorporate by reference information into this Registration Statement. This enables the Company to disclose important information to you by referring you to another document. Any information referred to in this way is considered part of this Registration Statement from the date the Company files such document. Any reports filed by the Company with the SEC after the date of this Registration Statement, and before the date that the offering of the securities by means of this Registration Statement is terminated, will automatically update and, where applicable, supersede any information contained in this Registration Statement or incorporated by reference in this Registration Statement.

We incorporate by reference into this Registration Statement the following documents or information filed with the SEC (other than, in each case, documents or information deemed to have been furnished under Item 2.02 or Item 7.01 of Form 8-K, which is not deemed filed in accordance with SEC rules and is not incorporated by reference herein):

The Company will provide without charge to each person, including any beneficial owner, to whom this Registration Statement is delivered, upon his or her written or oral request, a copy of any or all documents referred to above which have been or may be incorporated by reference into this Registration Statement, excluding exhibits to those documents unless they are specifically incorporated by reference into those documents. You can obtain those documents from our website at www.ajg.com or request them in writing or by telephone at the following address or telephone number: General Counsel, Arthur J. Gallagher & Co., 2850 W. Golf Road, Rolling Meadows, Illinois 60008-4050; Telephone: (630) 773-3800. Except for the information specifically incorporated into this Registration Statement by reference as set forth above, information contained on our website is not a part of this Registration Statement.

Item 4. Description of Securities.

Supplemental Savings and Thrift Plan (Supplemental Plan)

The Supplemental Plan is a non-qualified deferred compensation plan that allows certain highly compensated employees to defer a portion of their compensation until their retirement or a future date. The Company makes matching contributions to the Supplemental Plan (up to a maximum of the lesser of a participant’s elective deferral of base salary, annual bonus, quarterly bonuses and commissions or 5.0% of eligible compensation, less matching amounts contributed under the Company’s 401(k) plan).

The obligations of the Company under the Supplemental Plan (the “Supplemental Plan Obligations”) are unsecured general obligations of the Company to pay the compensation deferred in accordance with the terms of the Supplemental Plan, along with any interest deemed to accrue on the deferrals, and will rank equally with other unsecured and unsubordinated indebtedness of the Company from time to time outstanding.

The Compensation Committee of the Board of Directors establishes from time to time the hypothetical investment(s) made available under the Supplemental Plan, which may include investments in the Company’s common stock, for purposes of valuing participant accounts.

The Board of Directors of the Company reserves the right to amend or terminate the Supplemental Plan at any time.

The Supplemental Plan Obligations are not convertible into another security of the Company. The Supplemental Plan Obligations will not have the benefit of a negative pledge or any other affirmative or negative covenant on the part of the Company.

Item 5. Interests of Named Expert and Counsel.

Not applicable.

Item 6. Indemnification of Directors and Officers.

The Company is incorporated under the Delaware General Corporation Law (the “DGCL”).

Section 145(a) of the DGCL provides that a Delaware corporation shall have the power to indemnify any person who was or is a party or is threatened to be made a party to any threatened, pending or completed action, suit or proceeding, whether civil, criminal, administrative or investigative (other than an action by or in the right of the corporation) by reason of the fact that the person is or was a director, officer, employee or agent of the corporation, or is or was serving at the request of the corporation as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise, against expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by the person in connection with such action, suit or proceeding if the person acted in good faith and in a manner the person reasonably believed to be in or not opposed to the best interests of the corporation, and, with respect to any criminal action or proceeding, had no reasonable cause to believe the person’s conduct was unlawful.

Section 145(b) of the DGCL provides that a Delaware corporation shall have the power to indemnify any person who was or is a party or is threatened to be made a party to any threatened, pending or completed action or suit by or in the right of the corporation to procure a judgment in its favor by reason of the fact that such person acted in any of the capacities set forth above, against expenses (including attorneys’ fees) actually and reasonably incurred by the person in connection with the defense or settlement of such action or suit if the person acted under standards similar to those discussed above, except that no indemnification shall be made in respect of any claim, issue or matter as to which such person shall have been adjudged to be liable to the corporation unless and only to the extent that the Court of Chancery or the court in which such action or suit was brought shall determine that despite the adjudication of liability, such person is fairly and reasonably entitled to be indemnified for such expenses which the Court of Chancery or such other court shall deem proper.

Section 145 of the DGCL further provides that to the extent a current or former director or officer of a corporation has been successful on the merits or otherwise in defense of any action, suit or proceeding referred to in subsections (a) and (b) or in the defense of any claim, issue or matter therein, such person shall be indemnified against expenses (including attorneys’ fees) actually and reasonably incurred by such person in connection therewith; and that indemnification provided for by Section 145 shall not be deemed exclusive of any other rights to which the indemnified party may be entitled; and that the corporation shall have power to purchase and maintain insurance on behalf of a director or officer of the corporation against any liability asserted against such person and incurred by such person in any such capacity or arising out of such person’s status as such whether or not the corporation would have the power to indemnify such person against such liability under Section 145.

Section 102(b)(7) of the DGCL provides that a corporation may eliminate or limit the personal liability of a director or officer to the corporation or its stockholders for monetary damages for breach of fiduciary duty as a director or officer, provided that such provisions shall not eliminate or limit the liability of (1) a director for any breach of the director’s duty of loyalty to the corporation or its stockholders, (2) a director for acts or omissions not in good faith or that involve intentional misconduct or a knowing violation of law, (3) a director under section 174 of the DGCL; (4) for any transaction from which the director derived an improper personal benefit; or (5) an officer in any action by or in the right of the corporation. No such provision shall eliminate or limit the liability of a director for any act or omission occurring before the date when such provision becomes effective.

Article Seven of the Company’s Amended and Restated Bylaws and Article Twelfth of the Company’s Restated Certificate of Incorporation provide for the indemnification of each of the Company’s directors, officers, employees or agents to the full extent permitted by the DGCL or other applicable laws presently or hereafter in effect.

Article Seven of the Company’s Amended and Restated Bylaws provides that the Company shall indemnify any person in connection with any action, suit or proceeding brought or threatened by reason of the fact that he or she is or was one of the Company’s directors, officers, employees or agents, or is or was serving at the Company’s request as a director, officer, employee or agent of another enterprise, against all costs actually and reasonably incurred by him or her in connection with such action, suit or proceeding if he or she acted in good faith and in a manner he or she reasonably believed to be in or not opposed to the Company’s best interests and, with respect to any criminal action or proceeding, had no reasonable cause to believe his or her conduct was unlawful. Similar indemnity is permitted to be provided to such persons in connection with an action or suit by the Company or in the Company’s right, and provided further that such person shall not have been adjudged liable for negligence or misconduct in the performance of his or her duty to the Company, unless, in view of all the circumstances of the case, the court in which the action or suit was brought determines that such person despite the adjudication of liability is fairly and reasonably entitled to indemnity for such expenses.

Article Twelfth of the Company’s Restated Certificate of Incorporation eliminates the liability of the Company’s directors for monetary damages for breach of fiduciary duty as a director except where a director breaches his or her duty of loyalty to the Company and its stockholders, fails to act in good faith or engages in intentional misconduct or a knowing violation of law, authorizes the payment of a dividend or stock repurchase that

is illegal under Section 174 of the DGCL, or obtains an improper personal benefit. Article Twelfth of the Company’s Restated Certificate of Incorporation also eliminates the liability of the Company’s officers for monetary damages for breach of fiduciary duty as an officer except where an officer breaches his or her duty of loyalty to the Company and its stockholders, fails to act in good faith or engages in intentional misconduct or a knowing violation of law, obtains an improper personal benefit, or in any action by or in the right of the Company.

The Company also maintains and pays premiums on a directors’ and officers’ liability insurance policy and has entered into indemnity agreements with its directors and officers. The provisions of each indemnity agreement alter or clarify the statutory indemnification in the following respects: (1) indemnity will be explicitly provided for settlements in derivative actions; (2) prompt payment of litigation expenses will be provided in advance of indemnification; (3) prompt indemnification of advances of expenses will be provided unless a determination is made that the director or officer has not met the required standard; (4) the director or officer will be permitted to petition a court to determine whether his or her actions meet the standards required; and (5) partial indemnification will be permitted in the event that the director or officer is not entitled to full indemnification. In addition, each indemnity agreement specifically includes indemnification with respect to actions, suits or proceedings brought under and/or predicated upon the Securities Act of 1933, as amended, and/or the Securities Exchange Act of 1934, as amended.

The preceding summary is qualified in its entirety by the Company’s Restated Certificate of Incorporation and Amended and Restated Bylaws, and the indemnity agreements described above.

Item 7. Exemption from Registration Claimed.

Not applicable.

Item 8. Exhibits.

The Company will submit or has submitted the 401(k) Plan and any amendments thereto to the U.S. Internal Revenue Service (the “IRS”) in a timely manner in accordance with the agency’s regulations and has made or will make all changes required by the IRS in order to qualify the plan under Section 401 of the U.S. Internal Revenue Code of 1986, as amended.

Item 9. Undertakings.

(a) The undersigned registrant hereby undertakes:

(1) To file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement:

(i) To include any prospectus required by Section 10(a)(3) of the Securities Act of 1933;

(ii) To reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement. Notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the SEC pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than 20 percent change in the maximum aggregate offering price set forth in the “Calculation of Registration Fee” table in the effective registration statement; and

(iii) To include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement;

Provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) of this section do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the SEC by the registrant pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 that are incorporated by reference in the registration statement.

(2) That, for the purpose of determining any liability under the Securities Act of 1933, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(3) To remove from registration by means of a post-effective amendment any of the securities being registered that remain unsold at the termination of the offering.

(b) The undersigned registrant hereby undertakes that, for purposes of determining any liability under the Securities Act of 1933, each filing of the registrant’s annual report pursuant to Section 13(a) or Section 15(d) of the Securities Exchange Act of 1934 (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to Section 15(d) of the Securities Exchange Act of 1934) that is incorporated by reference in this registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(c) Insofar as indemnification for liabilities arising under the Securities Act of 1933 may be permitted to directors, officers and controlling persons of the registrant pursuant to the foregoing provisions, or otherwise, the registrant has been advised that in the opinion of the SEC such indemnification is against public policy as expressed in the Securities Act of 1933 and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Act and will be governed by the final adjudication of such issue.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Rolling Meadows, State of Illinois, on this 18th day of February, 2025.

POWER OF ATTORNEY

We, the undersigned directors and officers, do hereby severally constitute and appoint Walter D. Bay and Douglas K. Howell, and each of them severally, our true and lawful attorneys-in-fact and agents, to do any and all acts and things in our name and on our behalf in our capacities as directors and officers and to execute any and all instruments for us and in our names in the capacities indicated below, which said attorneys-in-fact and agents may deem necessary or advisable to enable Arthur J. Gallagher & Co. to comply with the Securities Act of 1933, as amended (the “Securities Act”), and any rules, regulations and requirements of the Securities and Exchange Commission, in connection with this registration statement on Form S-8, including specifically, but without limitation, power and authority to sign for us or any of us, in our names in the capacities indicated below, any and all amendments (including pre- and post- effective amendments) hereto and any related registration statement and amendments thereto; and we do each hereby ratify and confirm all that said attorneys-in-fact and agents shall do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act, this registration statement has been signed by the following persons in the capacities and on the dates indicated.

Exhibit 4.4

NOTICE OF RESTRICTED STOCK UNIT INDUCEMENT GRANT

BY MY ELECTRONIC ELECTION TO ACCEPT THE TERMS AND CONDITIONS OF THIS GRANT OF RESTRICTED STOCK UNITS (WHICH SERVES AS MY ELECTRONIC SIGNATURE OF THE AGREEMENT), I AGREE THAT MY AWARD IS GOVERNED BY THE PROVISIONS OF THIS AGREEMENT. (INCLUDING THE DELAWARE CHOICE OF GOVERNING LAW AND ITS OTHER TERMS AND CONDITIONS).

RESTRICTED STOCK UNIT INDUCEMENT AWARD AGREEMENT

This Restricted Stock Unit Inducement Award Agreement (this “Agreement”), dated as of the Grant Date set forth in the Notice of Restricted Stock Unit Grant attached hereto (the “Grant Notice”) is made between [•], a Delaware corporation (the “Company”), and the Participant set forth in the Grant Notice. The Grant Notice is included in and made part of this Agreement.

WHEREAS, as an inducement for the Participant to accept employment with the Company, the Company desires to grant to the Participant an “employment inducement award” under NYSE Rule 303A.08, outside of the [•] 2022 Long-Term Incentive Plan (the “Plan”), but desires that, except as expressly provided otherwise, the award granted hereunder be governed in a manner consistent with the terms and conditions of the Plan;

WHEREAS, the Company desires to evidence the award of restricted stock units to the Participant and to have the Participant acknowledge the terms and conditions of the award of restricted stock units by this Agreement; and

WHEREAS, the Compensation Committee of the Board of Directors of the Company (the “Committee”) or its delegate, as applicable, has approved this restricted stock unit award.

NOW, THEREFORE, IT IS AGREED:

1. Definitions. For purposes of this Agreement, the following terms shall have the meanings set forth below; other capitalized terms used in this Agreement shall have the meaning specified for such terms in the Plan, unless a different meaning is specified in this Agreement:

(a) “Cause” means, with respect to the Participant’s termination of employment, the following: (A) in the case where there is an employment agreement in effect between the Company or an affiliate of the Company and the Participant on the date hereof that defines “cause” (or words of like import), “cause” as defined under any such agreement, or (B) in the case where there is no employment agreement in effect between the Company or an affiliate of the Company and the Participant on the date hereof (or where there is such an agreement but it does not define “cause” (or words of like import)), termination due to: (i) the Participant’s gross negligence or the Participant’s continuing failure to perform the Participant’s duties and obligations for the Company or any of its subsidiaries or affiliates in any material respect or willful failure to follow lawful directions of the governing body that controls the Company, other than due to illness or incapacity or other Company-approved absences (including vacation); (ii) conduct causing the Company or any of its subsidiaries or affiliates material economic harm or substantial public disgrace; (iii) conviction of, indictment, or plea of “guilty” or “no contest” to, a felony or crime of moral turpitude; (iv) willful misconduct, fraud or embezzlement by the Participant involving the Company or any of its subsidiaries or affiliates, or any theft, misrepresentation or dishonesty by the Participant involving the Company or any of its subsidiaries or affiliates intended to result in personal enrichment of the Participant; (v) unauthorized use or disclosure of proprietary information of the Company or any of its subsidiaries or affiliates, which use or disclosure causes material harm to the Company (except with respect to the reporting possible violations of federal law or regulation to, participating in any investigation by, providing information to or cooperating with any governmental agency, regulator or entity or making other disclosures that are protected under the whistle blower provisions of applicable law or regulation and/ or for the purpose of reporting or investigating a suspected violation of law); or (vi) the Participant’s material violation of any material written policies of the Company or any of its subsidiaries or affiliates applicable to the Participant, or any violation of any restrictive covenants agreement with the Company or any of its subsidiaries or affiliates; provided that the Participant must be provided with written notice of the Participant’s termination for “Cause” (including an explanation of the basis for “Cause”) and, solely with respect to clauses (i) and (vi), to the extent curable, the Participant must be provided with a 30-day period following the Participant’s receipt of such notice to cure the event(s) that trigger Cause and the Company shall make the final determination in good faith as to whether the Participant have cured the existence of Cause.

(b) “Company” shall mean the Company and any corporation 50% or more of the stock of which is beneficially owned directly by the Company or indirectly through another corporation or corporations in which the Company is the beneficial owner of 50% or more of the stock.

(c) “Disability” shall have the meaning given to the term “Long-Term Disability” under the [•] Long-Term Disability Insurance Plan, as amended from time to time, or such successor long-term disability plan under which the Participant is covered at the time of determination.

(d) “Good Reason” means any of the following events occur without the Participant’s consent: (i) the permanent relocation of the Participant’s primary place of employment by more than 50 miles from the Participant’s current principal place of employment; (ii) a reduction in the Participant’s base salary and annual target bonus opportunity by an aggregate amount that is in excess of twenty percent (20%) of the Participant’s then-current base salary and annual target bonus opportunity; or (iii) a material and adverse change in the Participant’s functional role with the Company or affiliates (i.e., management, sales, accounting, treasury, legal, HR, etc.), it being understood and agreed that Good Reason will not exist (A) as a result of a change in job title or reporting duties or responsibilities (including any requirement that the Participant report to an individual at the Company or any of its affiliates) or (B) if the Company determines in good faith after a reasonable review of the relevant facts identified by the Participant that the Participant’s functional role with the Company and its subsidiaries or affiliates at the time in question (excluding job title and reporting duties and responsibilities) is substantially consistent with the Participant’s functional role with the Company and its subsidiaries on the date hereof. To be considered a resignation from employment on account of Good Reason, the Participant must provide written notice to the Company (stating that the Participant believes one or more of the Good Reason conditions described above exists) within 60 days following the Participant’s knowledge of the initial existence of such condition, the Company shall have 60 days to cure such circumstances alleged to constitute Good Reason, and the Participant must resign within 30 days following the Company’s failure to cure such condition.

(e) “Potential Target” means any business with which the Company or any of its subsidiaries or affiliates has, directly or indirectly, entertained discussions or requested and received information relating to the actual or potential acquisition of such business by the Company or any of its subsidiaries or affiliates within the two-year period immediately preceding the date of the termination of the Participant’s employment with the Company or one of its subsidiaries or affiliates for any reason.

(f) “Restricted Period” means the period beginning on the Grant Date and ending two years after the earlier to occur of (i) any termination of the Participant’s employment with the Company or one of its subsidiaries or affiliates for any reason and (ii) the second anniversary of the Grant Date.

(g) “Section 409A” means Section 409A of the Code, and the Treasury Regulations promulgated and other official guidance issued thereunder.

(h) “Shares” shall mean shares of Common Stock of the Company.

(i) “Termination of Employment” means a “separation from service” as defined under Section 409A, as determined in accordance with the Company’s Policy Regarding Section 409A Compliance.

2. Grant of Restricted Stock Units. Subject to the terms and conditions of this Agreement, the Company hereby grants to the Participant, the Number of Shares Underlying Restricted Stock Units set forth in the Grant Notice (the “Restricted Stock Units”). Subject to the provisions of this Agreement, the grant of Restricted Stock Units may not be revoked.

3. Dividend Equivalents. An account established by the Company on behalf of the Participant shall be credited with the amount of all dividends that would have been paid on the Restricted Stock Units if such shares were actually held by the Participant (“Dividend Equivalents”). Such Dividend Equivalents shall be subject to the same Restriction Period applicable to the Restricted Stock Units to which they relate, and as soon as administratively practicable following the lapse of the Restriction Period applicable to a Restricted Stock Unit, but in no event later than 74 days following such date, the Dividend Equivalents related to such unit shall be paid to the Participant in cash, without earnings thereon.

4. Restriction Period; Termination. The Restriction Period with respect to the Restricted Stock Units shall be as set forth in the Grant Notice. In order to earn and vest in the Restricted Stock Units, the Participant must at the time of vesting remain employed by the Company and not subject to notice of termination of employment (whether given by the Company or the Participant). Subject to the terms of this Agreement, all Restricted Stock Units for which the Restriction Period had not lapsed prior to the date of the Participant’s termination of employment (or the issuing of notice of termination, if earlier) shall be immediately forfeited; provided, however, that upon termination of the Participant’s employment due to death, then the Restriction Period shall immediately lapse as to the full number of Restricted Stock Units and such Restricted Stock Units will be settled in accordance with Section 5; provided, further, that in the event the Company or any affiliate thereof terminates the Participant employment for a reason other than Cause, the Participant terminates the Participant’s employment with Good Reason, or the Participant’s employment is terminated due to Disability, in each case, prior to the second anniversary of the Grant Date, and provided the Participant timely executes (and does not revoke) a customary release of claims, the Restricted Stock Units shall vest but shall be settled in accordance with the Vesting Dates set forth in the Notice.

5. Payment of Restricted Stock Units. Within 30 days following each Vesting Date applicable to the Restricted Stock Units,, the vested Shares underlying the vested Restricted Stock Units, free of all restrictions, shall be issued or delivered to the Participant or his or her beneficiary or estate, as the case may be. Upon issuance, the Shares will be electronically transferred to an account in the Participant’s name at the provider then administering the Restricted Stock Units.

6. Recapitalization. In the event of a recapitalization, stock split, stock dividend, combination or exchange of shares, merger, consolidation, rights offering, separation, reorganization or liquidation, or any other change in the corporate structure or shares of the Company, the Committee shall make such equitable adjustments, designed to protect against dilution, as it may deem appropriate in the number and kind of shares covered hereby.

7. Compliance with Laws and Regulations. The Company shall not be obligated to issue any Shares pursuant to this Agreement unless the Shares are at that time effectively registered or exempt from registration under the Securities Act of 1933, as amended, and, as applicable, local and foreign laws.

8. Acceptance of Benefits. By accepting any benefit under this Agreement, the Participant and any person claiming under or through the Participant shall be conclusively deemed to have indicated his or her acceptance and ratification of, and consent to, all of the terms and conditions of this Agreement. Unless defined herein, capitalized terms are used herein as defined in the Plan. This Agreement is subject to such rules, policies and regulations as may from time to time be adopted by the Committee. All good faith determinations and interpretations made by the Committee with regard to any question arising hereunder shall be binding and conclusive on the Participant and on his or her legal representatives and beneficiaries.

9. Tax Withholding.

(a) Regardless of any action the Company takes with respect to any or all income tax (including U.S. federal, state and local taxes and/or non-U.S. taxes), social insurance, payroll tax, payment on account or other tax-related withholding (“Tax-Related Items”), the Participant acknowledges that the ultimate liability for all Tax-Related Items legally due by the Participant is and remains the Participant’s responsibility and that the Company (a) makes no representations or undertakings regarding the treatment of any Tax-Related Items in connection with any aspect of the Restricted Stock Units, including the grant of the Restricted Stock Units, the vesting of the Restricted Stock Units, the subsequent sale of any Shares acquired pursuant to the Restricted Stock Units and the receipt of any dividends or dividend equivalents; and (b) does not commit to structure the terms of the grant or any aspect of the Restricted Stock Units to reduce or eliminate the Participant’s liability for Tax-Related Items. Further, if the Participant becomes subject to taxation in more than one country between the Grant Date and the date of any relevant taxable or tax withholding event, as applicable, the Participant acknowledges that the Company may be required to withhold or account for Tax-Related Items in more than one country. For tax and withholding purposes and unless otherwise required under applicable law, the value of any Shares issued shall be determined based on the closing stock price on the date of vesting regardless of when the Shares are actually credited to the Participant’s account.

(b) If the Participant’s country of residence (and/or the country of employment, if different) requires withholding of Tax-Related Items, the Company shall, unless otherwise timely requested by the Participant in writing pursuant to the Company’s procedures, withhold a portion of the Shares otherwise issuable upon vesting of the Restricted Stock Units (or a portion of any cash proceeds where the Restricted Stock Units are settled in cash) that have an aggregate Fair Market Value sufficient to pay the Tax-Related Items required to be withheld with respect to the Shares; provided, that the Company shall have a right to implement such Share withholding in the event the Participant makes such a request but does not timely deliver payment. For purposes of the foregoing, no fractional Shares will be withheld or issued pursuant to the grant of the Restricted Stock Units and the issuance of Shares hereunder. If the obligation for Tax-Related Items is satisfied by withholding Shares or a portion of any cash proceeds (where the Restricted Stock Units are settled in cash or a forced sale is required), for tax purposes, the Participant shall be deemed to have been issued the full number of Shares subject to the vested Restricted Stock Units, notwithstanding that a number of the Shares (or a portion of any cash proceeds) are withheld solely for the purpose of satisfying any withholding obligations for the Tax-Related Items due as a result of any aspect of this Agreement. The Company may withhold any amount necessary to pay the Tax-Related Items from the Participant’s regular salary or other amounts payable to the Participant or may require the Participant to submit payment equivalent to the Tax-Related Items required to be withheld with respect to the Shares by means of certified check, cashier’s check or wire transfer. In the event the withholding requirements are not satisfied, no Shares will be issued to the Participant (or the Participant’s estate) upon vesting of the Restricted Stock Units (or no cash payment will be made where the Restricted Stock Units are settled in cash or a forced sale is required) unless and until satisfactory arrangements (as determined by the Company in its sole discretion) have been made by the Participant with respect to the payment of any such Tax-Related Items. By accepting the Restricted Stock Units, the Participant expressly consents to the methods of withholding as provided hereunder and/or any other methods of withholding that the Company may adopted and are permitted under the Plan to meet the withholding and/or other requirements as provided under applicable laws, rules and regulations. All other Tax-Related Items related to the Restricted Stock Units and any Shares delivered in payment thereof shall be the Participant’s sole responsibility.

(c) To the extent the Company pays any Tax-Related Items that are the Participant’s responsibility (“Advanced Tax Payments”), the Company shall be entitled to recover such Advanced Tax Payments from the Participant in any manner that the Company determines appropriate in its sole discretion. For purposes of the foregoing, the manner of recovery of the Advanced Tax Payments shall include (but is not limited to) offsetting the Advanced Tax Payments against any and all amounts that may be otherwise owed to the Participant by the Company (including regular salary/wages, bonuses, incentive payments and Shares acquired by the Participant pursuant to any equity compensation plan that are otherwise held by the Company for the Participant’s benefit).

(d) The Company may, in the discretion of the Committee, provide for alternative arrangements to satisfy applicable tax withholding requirements in accordance with Section 6.5 of the Plan.

10. Non-Transferability. Until the Restricted Period has lapsed, the Restricted Stock Units may not be transferred, assigned, pledged, or otherwise encumbered or disposed of other than by will or the laws of descent and distribution; provided, however, that the Committee may, in its discretion, permit the Restricted Stock Units to be transferred subject to such conditions and limitations as the Committee may impose.

11. No Right to Continued Employment. The Company is not obligated by or as a result of this Agreement to continue the Participant’s employment, and this Agreement shall not interfere in any way with the right of the Company to terminate the employment of the Participant at any time.

12. Nature of Grant. In accepting this grant of Restricted Stock Units, the Participant acknowledges that:

In addition, the following provisions apply if the Participant is providing services outside the United States:

13. No Rights as a Stockholder. The Participant shall not have a beneficial ownership interest in, or any of the rights and privileges of a stockholder as to, the Shares underlying the Restricted Stock Units, including the right to receive dividends and the right to vote such Shares underlying the Restricted Stock Units until such Restricted Stock Units vest and Shares are issued and transferred to the Participant in accordance with the terms of this Agreement. The Participant shall not be entitled to delivery of the Shares subject to the Restricted Stock Units award, or to the Dividend Equivalents related to such units, until the units have vested.

14. Notice and Consent to Transfer Personal Data. Pursuant to applicable personal data protection laws, the Company hereby notifies the Participant of the following in relation to the Participant’s personal data and the collection, processing and transfer of such data in relation to the Company’s grant of the Restricted Stock Units. The collection, processing and transfer of the Participant’s personal data is necessary for the Company’s administration of this Agreement. The Participant’s denial and/or objection to the collection, processing and transfer of personal data may affect the Participant’s award hereunder. As such, the Participant voluntarily acknowledges and consents (where required under applicable law) to the collection, use, processing and transfer of personal data as described herein.

The Company holds certain personal information about the Participant, including the Participant’s name, home address and telephone number, date of birth, social security number or other employee identification number, salary, nationality, job title, any Shares or directorships held in the Company, details of all options or any other entitlement to Shares awarded, canceled, purchased, vested, unvested or outstanding in the Participant’s favor, for the purpose of managing and administering this Agreement (“Data”). The Data may be provided by the Participant or collected, where lawful, from third parties, and the Company will process the Data for the sole and exclusive purpose of implementing, administering and managing the Participant’s rights hereunder. The Data processing will take place through electronic and non-electronic means according to logics and procedures strictly correlated to the purposes for which Data are collected and with confidentiality and security provisions as set forth by applicable laws and regulations in the Participant’s country of residence. Data processing operations will be performed minimizing the use of personal and identification data when such operations are unnecessary for the processing purposes sought. Data will be accessible within the Company’s organization only by those persons requiring access for purposes of the implementation, administration and operation of this Agreement.

The Company will transfer Data internally as necessary for the purpose of implementation, administration and management of the Participant’s award hereunder, and the Company may further transfer Data to any third parties assisting the Company in the implementation, administration and management of this Agreement. These recipients may be located in the European Economic Area, or elsewhere throughout the world, such as the United States. The Participant hereby authorizes (where required under applicable law) for them to receive, possess, use, retain and transfer the Data, in electronic or other form, for purposes of implementing, administering and managing the Participant’s participation hereunder, including any requisite transfer of such Data as may be required for the administration of this Agreement and/or the subsequent holding of Shares on the Participant’s behalf to a broker or other third party with whom the Participant may elect to deposit any Shares acquired hereunder.

The Participant may, at any time, exercise their rights provided under applicable personal data protection laws, which may include the right to (a) obtain confirmation as to the existence of the Data, (b) verify the content, origin and accuracy of the Data, (c) request the integration, update, amendment, deletion, or blockage (for breach of applicable laws) of the Data, and (d) to oppose, for legal reasons, the collection, processing or transfer of the Data which is not necessary or required for the implementation, administration and/or operation of this Agreement. The Participant may seek to exercise these rights by contacting the Company’s human resource department.

15. Notices. Notices hereunder shall be mailed or delivered to the Company at its principal place of business and shall be mailed or delivered to the Participant at the address on file with the Company or, in either case, at such other address as one party may subsequently furnish to the other party in writing.

16. Other Plans. The Participant acknowledges that any income derived from the lapse of the Restriction Period applicable to the Restricted Stock Units shall not affect the Participant’s participation in, or benefits under, any other benefit plan or other contract or arrangement maintained by the Company.

17. 409A. This Agreement and the Restricted Stock Units are intended to comply with the requirements of Section 409A, so as to prevent the inclusion in gross income of any benefits accrued hereunder in a taxable year prior to the taxable year or years in which such amount would otherwise be actually distributed or made available to the Participant. Each payment under this Agreement shall constitute a “separately identified” amount within the meaning of Treasury regulation §1.409A-2(b)(2). This Agreement and the Restricted Stock Units shall be administered and interpreted in a manner consistent with this intent and the Company’s Policy Regarding Section 409A Compliance. If the Company determines that it has failed to comply with the requirements of Section 409A, the Company may, in its sole discretion, and without the Participant’s consent, amend this Agreement to cause it to comply with or be exempt from Section 409A.

18. Restrictive Covenants.

(a) Obligation to Maintain Confidentiality. The Participant acknowledges that the information, observations and data (including trade secrets) obtained by the Participant during the course of the Participant’s employment with the Company or its subsidiaries or its affiliates concerning the business or affairs of the Company and its subsidiaries and affiliates (“Confidential Information”) are the property of the Company and such subsidiaries and affiliates, including information concerning acquisition opportunities in or reasonably related to the Company’s and its subsidiaries’ and affiliates’ business or industry of which the Participant becomes aware during the course of the Participant’s employment. Therefore, the Participant agrees that the Participant will not disclose to any unauthorized person or use for the Participant’s own account any Confidential Information without the written consent of the Board, unless and to the extent that the Confidential Information, (i) becomes generally known to and available for use by the public other than as a result of the Participant’s acts or omissions to act or (ii) is required to be disclosed pursuant to any applicable law or court order. Nothing in this Agreement shall prohibit or impede the Participant from communicating, cooperating or filing a complaint with any U.S. federal, state or local governmental or law enforcement branch, agency or entity (collectively, a “Governmental Entity”) with respect to possible violations of any U.S. federal, state or local law or regulation, or otherwise making disclosures to any Governmental Entity, in each case, that are protected under the whistleblower provisions of any such law or regulation, provided that in each case such communications and disclosures are consistent with applicable law. The Participant does not need the prior authorization of (or to give notice to) the Company regarding any such communication or disclosure. Notwithstanding the foregoing, under no circumstance is the Participant authorized to disclose any information covered by the Company’s or its affiliates’ attorney-client privilege or attorney work product or the Company’s trade secrets without prior written consent of the Company’s General Counsel.

(b) Nonsolicitation. The Participant acknowledges that during the course of the Participant’s employment with the Company or one of its subsidiaries or affiliates, the Participant has and will continue to become familiar with the Company’s and its subsidiaries’ and affiliates’ trade secrets and with other confidential information concerning the Company and such subsidiaries and affiliates and that the Participant’s services will be of special, unique and extraordinary value to the Company and its subsidiaries and affiliates. Therefore, the Participant agrees that during the Restricted Period, the Participant will not directly or indirectly through another entity (i) induce or attempt to induce any employee of the Company or any of its subsidiaries or affiliates to leave the employ of the Company or such subsidiary or affiliate, or in any way interfere with the relationship between the Company or any of its subsidiaries or affiliates and any employee thereof, (ii) hire any employee of the Company or any of its subsidiaries or affiliates or hire any former employee of the Company or any of its subsidiaries or affiliates within one year after such person ceased to be an employee of the Company or any of its subsidiaries or affiliates, (iii) induce or attempt to induce any Potential Target, customer, supplier, licensee or other business relation of the Company or any of its subsidiaries or affiliates to cease doing or not do business with the Company or such subsidiary or affiliate or in any way interfere with the relationship between any such Potential Target, customer, supplier, licensee or business relation and the Company or any such subsidiary or affiliate or (iv) directly or indirectly acquire, attempt to acquire, or directly or indirectly arrange, participate in or facilitate (including, without limitation, by providing any assistance, advice, solicitation, brokerage or similar services) any acquisition by another person of, any Potential Target.

(c) Enforcement. If, at the time of enforcement of the covenants set forth in this Agreement, a court holds that the restrictions stated herein are unreasonable under circumstances then existing, the parties hereto agree that the maximum duration or scope reasonable under such circumstances shall be substituted for the stated period or scope and that the court shall be allowed to revise the restrictions contained herein to cover the maximum duration, scope and area permitted by law. Because the Participant’s services are unique and because the Participant has access to confidential information, the parties hereto agree that money damages would be an inadequate remedy for any breach of this Agreement. Therefore, in the event a breach or threatened breach of this Agreement, the Company, its subsidiaries and/or their respective successors or assigns may, in addition to other rights and remedies existing in their favor, apply to any court of competent jurisdiction for specific performance and/or injunctive or other relief in order to enforce, or prevent any violations of, the provisions hereof (without posting a bond or other security). In the event that the Participant breaches any provision of this Agreement, then the Restricted Period shall be extended for a period of time equal to the period of time during which such breach occurred and, in the event that the Company or any of its subsidiaries or affiliates is required to seek relief from such breach in any court, then the Restricted Period shall be extended for a period of time equal to the pendency of such proceedings, including all appeals.

(d) Additional Acknowledgments. The Participant acknowledges that the provisions of this Agreement are in consideration of: (i) the Restricted Stock Units granted hereunder and (ii) additional good and valuable consideration as set forth in this Agreement. In addition, the Participant agrees and acknowledges that the restrictions contained in this Agreement do not preclude the Participant from earning a livelihood, nor do they unreasonably impose limitations on the Participant’s ability to earn a living. The Participant agrees and acknowledges that the potential harm to the Company and its subsidiaries and affiliates of the non-enforcement of any provision of this Section 18 outweighs any potential harm to the Participant of its enforcement by injunction or otherwise. The Participant acknowledges that the Participant has carefully read this Agreement and consulted with legal counsel of the Participant’s choosing regarding its contents, have given careful consideration to the restraints imposed upon the Participant by this Agreement and is in full accord as to their necessity for the reasonable and proper protection of confidential and proprietary information of the Company and its subsidiaries now existing or to be developed in the future. The Participant expressly acknowledges and agrees that each and every restraint imposed by this Agreement is reasonable with respect to subject matter and time period.

19. Governing Law. This Agreement shall be governed by the laws of the State of Delaware and construed in accordance therewith without giving effect to principles of conflicts of laws.

20. Insider Trading. The Participant acknowledges that, depending on Participant’s or the Participant’s broker’s country of residence or where the Company shares are listed, the Participant may be subject to insider trading restrictions and/or market abuse laws which may affect the Participant’s ability to accept, acquire, sell or otherwise dispose of Company shares, rights to shares or rights linked to the value of shares during such times the Participant is considered to have “inside information” regarding the Company as defined in the laws or regulations in the Participant’s country. Local insider trading laws and regulations may prohibit the cancellation or amendment of orders the Participant placed before the Participant possessed inside information. Furthermore, the Participant could be prohibited from (i) disclosing the inside information to any third party (other than on a “need to know” basis) and (ii) “tipping” third parties or causing them otherwise to buy or sell securities. Third parties includes fellow employees. Any restrictions under these laws or regulations are separate from and in addition to any restrictions that may be imposed under the Company’s Insider Trading Policy and Global Standards of Business Conduct. The Participant acknowledges that it is the Participant’s responsibility to comply with any restrictions and is advised to speak to the Participant’s personal advisor on this matter.

21. Exchange Controls. As a condition to this grant of Restricted Stock Units, the Participant agrees to comply with any applicable foreign exchange rules and regulations.

22. Electronic Delivery. The Company may, in its sole discretion, decide to deliver any documents related to this Agreement by electronic means. The Participant hereby consents to receive such documents by electronic delivery receive correspondence through an on-line or electronic system established and maintained by the Company or a third party designated by the Company.

23. Severability. The invalidity or unenforceability of any provision of this Agreement shall not affect the validity or enforceability of any other provision of this Agreement, and each other provision of this Agreement shall be severable and enforceable to the extent permitted by law. To the extent a court or tribunal of competent jurisdiction determines that any provision of this Agreement is invalid or unenforceable, in whole or in part, the Company, in its sole discretion, shall have the power and authority to revise or strike such provision to the minimum extent necessary to make it valid and enforceable to the full extent permitted under local law.

24. Entire Agreement. This Agreement and the Grant Notice constitute the entire agreement between the Participant and the Company regarding the award of Restricted Stock Units and supersede all prior and contemporaneous agreements and understandings, oral or written, between the parties regarding the award, including any retention bonus letter agreement to which the Participant is a party that was dated prior to the Grant Date.

25. Language. The Participant acknowledges and represents that the Participant is sufficiently proficient in the English language, or has consulted with an advisor who is sufficiently proficient in the English language, so as to enable the Participant to understand the provisions of this Agreement, Grant Notice and the Plan. If the Participant has received this Agreement, Grant Notice or any other document related to the Plan translated into a language other than English and if the meaning of the translated version is different than the English version, the English version will control.

26. Change in Control. Upon the occurrence of a Change in Control, as defined in the Plan, this Agreement and all Restricted Stock Units granted hereunder shall governed by Section 4.8 of the Plan. If applicable, payment under this Section 26 shall be made as soon as administratively practicable following the Change in Control, but in no event later than 75 days thereafter; provided, however, if the Change in Control is not a “change in control event” within the meaning of Section 409A of the Code, then the Restricted Stock Units shall be settled in accordance with the normal Vesting Dates, subject to acceleration in the event of the Participant’s death.

IN WITNESS WHEREOF, the parties have executed and delivered this Agreement as of the day and year first above written.

Exhibit 5.1

February 18, 2025

Arthur J. Gallagher & Co.

2850 W. Golf Road

Rolling Meadows, Illinois 60008-4050

Ladies and Gentlemen:

We have examined the Registration Statement on Form S-8 (the “Registration Statement”) of Arthur J. Gallagher & Co., a Delaware corporation (the “Company”), to be filed with the Securities and Exchange Commission under the Securities Act of 1933, as amended (the “Securities Act”), in connection with the offering by the Company of up to (i) 1,000,000 shares of the Company’s common stock, par value $1.00 per share (the “Common Stock”), available for issuance under the Arthur J. Gallagher & Co. Employees’ 401(k) Savings and Thrift Plan (the “401(k) Plan”), (ii) 100,000 shares of Common Stock available for issuance pursuant to the Arthur J. Gallagher & Co. Supplemental Savings and Thrift Plan (the “Supplemental Plan”), and (iii) 1,200,000 shares of Common Stock issuable upon the vesting of restricted stock unit inducement awards (the “RSU Inducement Awards” and together with the Supplemental Plan and the 401(k) Plan, the “Plans”).

In arriving at the opinion expressed below, we have examined originals, or copies certified or otherwise identified to our satisfaction as being true and complete copies of the originals, of the appliable Plans and such other documents, corporate records of the Company, certificates of officers of the Company and of public officials and other documents as we have deemed necessary or advisable to enable us to render this opinion. In our examination, we have assumed without independent investigation the genuineness of all signatures, the legal capacity and competency of all natural persons, the authenticity of all documents submitted to us as originals and the conformity to original documents of all documents submitted to us as copies. We have also assumed that there are no agreements or understandings between or among the Company and any participants in the Plans that would expand, modify or otherwise affect the terms of the Plans or the respective rights or obligations of the participants thereunder. Finally, we have assumed the accuracy of all other information provided to us by the Company during the course of our investigations, on which we have relied in issuing the opinion expressed below

Based upon the foregoing, and subject to the assumptions, exceptions, qualifications and limitations set forth herein and in reliance on the statements of fact contained in the documents that we have examined, we are of the opinion that the shares of Common Stock, when issued and sold in accordance with the terms set forth in the Plans and against payment therefore, and when the Registration Statement has become effective under the Securities Act, will be validly issued, fully paid and non-assessable.

We render no opinion herein as to matters involving the laws of any jurisdiction other than the Delaware General Corporation Law (the “DGCL”). This opinion is limited to the effect of the current state of the DGCL and to the facts as they currently exist. We assume no obligation to revise or supplement this opinion in the event of future changes in such laws or the interpretations thereof or such facts.

Gibson, Dunn & Crutcher LLP

333 South Grand Avenue | Los Angeles, CA 90071-3197 | T: 213.229.7000 | F: 213.229.7520 | gibsondunn.com

February 18, 2025

Page 2

We consent to the filing of this opinion as an exhibit to the Registration Statement. In giving these consents, we do not thereby admit that we are within the category of persons whose consent is required under Section 7 of the Securities Act or the Rules and Regulations of the Commission.

Very truly yours,

/s/ Gibson, Dunn & Crutcher LLP

Gibson, Dunn & Crutcher LLP

Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in the Registration Statement (Form S-8 No. 333-000000) pertaining to the Arthur J. Gallagher & Co. Employees’ 401(k) Savings and Thrift Plan, Arthur J. Gallagher & Co. Supplemental Savings and Thrift Plan, and Stand Alone Restricted Stock Unit Inducement Awards of our reports dated February 17, 2025, with respect to the consolidated financial statements of Arthur J. Gallagher & Co. and the effectiveness of internal control over financial reporting of Arthur J. Gallagher & Co. included in its Annual Report (Form 10-K) for the year ended December 31, 2024, filed with the Securities and Exchange Commission.

/s/ Ernst & Young LLP

Chicago, Illinois

February 18, 2025