AJG Arthur J Gallagher and Company

As filed with the Securities and Exchange Commission on February 12, 2024

Registration No. 333-   

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-3

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

ARTHUR J. GALLAGHER & CO.

(Exact name of registrant as specified in its charter)

2850 Golf Road

Rolling Meadows, Illinois

60008-4050

(630) 773-3800

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Walter D. Bay, Esq.

Vice President, General Counsel and Secretary

Arthur J. Gallagher & Co.

2850 Golf Road

Rolling Meadows, Illinois 60008-4050

(630) 773-3800

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

COPIES TO:

Approximate date of commencement of proposed sale of the securities to the public: From time to time after this registration statement becomes effective.

If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box. ☐

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box. ☒

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a registration statement pursuant to General Instruction I.D. or a post-effective amendment thereto that shall become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act, check the following box. ☒

If this Form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box. ☐

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 Securities Exchange Act of 1934, as amended (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 Securities Act. ☐

PROSPECTUS

DEBT SECURITIES

GUARANTEES

COMMON STOCK

PREFERRED STOCK

WARRANTS

DEPOSITARY SHARES

PURCHASE CONTRACTS

UNITS

We may from time to time offer to sell our debt securities, guarantees of debt securities, common stock or preferred stock, either separately or represented by warrants, depositary shares or purchase contracts, as well as units that include any of these securities or securities of other entities. The debt securities may consist of debentures, notes or other types of debt. We may also use this prospectus from time to time to register these securities that may be offered and sold by selling securityholders.

Each time we sell securities pursuant to this prospectus, we will provide a prospectus supplement and attach it to this prospectus. The prospectus supplement will contain more specific information about the terms of that offering. The prospectus supplement may also add, update or change information contained in this prospectus. This prospectus may not be used to offer or sell these securities without a prospectus supplement describing the method and terms of the offering. You should carefully read this prospectus and any accompanying prospectus supplement, together with the information we incorporate by reference, before you make your investment decision.

We may sell these securities on a continuous or delayed basis directly, through agents or underwriters designated from time to time or through a combination of these methods. For additional information on the method of sale, you should refer to the section of this prospectus entitled “Plan of Distribution” on page 10. We reserve the sole right to accept, and together with any agents, dealers and underwriters, reserve the right to reject, in whole or in part, any proposed purchase of these securities. If any agents, dealers or underwriters are involved in the sale of these securities, the applicable prospectus supplement will set forth the names and any applicable commissions or discounts.

Our common stock is traded on the New York Stock Exchange under the symbol “AJG.”

Investing in these securities involves risks. You should carefully read and consider the risks referenced under “Risk Factors” beginning on page 3 of this prospectus for a discussion of the factors you should carefully consider, as well as the other information contained in or incorporated by reference in this prospectus or in any accompanying prospectus supplement, in determining whether to invest in these securities.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is February 12, 2024.

TABLE OF CONTENTS

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ABOUT THIS PROSPECTUS

This prospectus is part of a “shelf” registration statement on Form S-3 that we filed with the Securities and Exchange Commission, or SEC. Under the shelf registration process, we may from time to time, offer and sell the securities described in this prospectus or use this prospectus to register securities that may be offered and sold by selling securityholders from time to time. This prospectus provides a general description of the securities that we may offer and sell and that may be offered and sold by selling securityholders. Each time we offer and sell these securities, we will provide a prospectus supplement containing specific information about the terms of the securities being offered and the manner in which it may be offered. We may add, update or change the information contained in this prospectus by means of one or more prospectus supplements. If there is any inconsistency between the information in this prospectus and the applicable prospectus supplement, you should rely on the information in the prospectus supplement. Before investing in our securities, both this prospectus and any prospectus supplement, together with the additional information described under the headings “Where You Can Find More Information” and “Incorporation of Certain Information by Reference,” should be carefully reviewed.

You should rely only on information contained in or incorporated by reference in this prospectus. We have not authorized anyone to give you any information or make any representation that is different from, or in addition to, that contained in this prospectus or in any of the materials that we have incorporated by reference into this document. If you are in a jurisdiction where offers to sell, or solicitations of offers to purchase, the securities offered by this document are unlawful, or if you are a person to whom it is unlawful to direct these types of activities, then the offer presented in this document does not extend to you. The information contained in this prospectus (including the information contained in any document incorporated by reference in this prospectus) speaks only as of the date of each such document, unless the information specifically indicates that another date applies.

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ARTHUR J. GALLAGHER & CO.

We are engaged in providing insurance brokerage, reinsurance brokerage, consulting services, and third-party property/casualty claims settlement and administration services to entities and individuals in the U.S. and abroad.

We report our results in three segments: brokerage, risk management and corporate. Brokerage and risk management contributed approximately 86% and 14%, respectively, to 2023 revenues. We generate approximately 64% of our revenues for the combined brokerage and risk management segments domestically, with the remaining 36% generated internationally, primarily in the Australia, Canada, New Zealand and the U.K. The corporate segment did not generate revenues in 2023. Our ability to generate tax credits from qualified refined coal pursuant to Internal Revenue Code Section 45 ended in December 2021, and in 2022 we ran off existing chemical supplies as part of the wind down of such investments’ operations, which generated some revenues. Our major sources of operating revenues are commissions, fees and supplemental and contingent revenues from our brokerage operation, and fees including performance-based fees, from risk management operations.

For more information about our business, please refer to the “Business” section in our most recent Annual Report on Form 10-K filed with the SEC and incorporated by reference in this prospectus and the “Management’s Discussion and Analysis of Financial Condition and Results of Operations” sections of our most recent Annual Report on Form 10-K and all subsequent Quarterly Reports on Form 10-Q filed with the SEC and incorporated by reference in this prospectus.

Shares of our common stock are traded on the New York Stock Exchange under the symbol “AJG”. We were reincorporated as a Delaware corporation in 1972. Our executive offices are located at 2850 Golf Road, Rolling Meadows, Illinois 60008-4050, and our telephone number is (630) 773-3800.

Unless the context otherwise requires, the terms “we,” “our,” “Gallagher”, and “us” refer to Arthur J. Gallagher & Co. and/or its subsidiaries, as appropriate. The term “you” refers to a prospective investor.

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RISK FACTORS

Investing in our securities involves risks. Before making an investment decision regarding our securities, in addition to the other information, documents or reports included in or incorporated by reference into this prospectus and any accompanying prospectus supplement or other offering materials, you should carefully consider the specific risks set forth under the caption “Risk Factors” in the applicable prospectus supplement as well as our Annual Report on Form 10-K for the fiscal year ended December 31, 2023, which is incorporated by reference into this prospectus and any prospectus supplement, in their entirety, as the same may be amended, supplemented or superseded from time to time by our filings under the Exchange Act of 1934, as amended (the “Exchange Act”). For more information, see the section entitled “Where You Can Find More Information.” If any one or more of the risks set forth in the applicable prospectus supplement or documents incorporated by reference into this prospectus occur, they could materially and adversely affect our business, financial condition or results of operations. Consequently, the trading price of our securities could decline, and you may lose all or part of your investment.

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CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

This prospectus, the accompanying prospectus supplement and the documents they incorporate by reference, contain certain statements related to future results, or state our intentions, beliefs and expectations or predictions for the future, which are forward-looking statements as that term is defined in the Private Securities Litigation Reform Act of 1995. Forward-looking statements relate to expectations or forecasts of future events. Such statements use words such as “anticipate,” “believe,” “estimate,” “expect,” “contemplate,” “forecast,” “project,” “intend,” “plan,” “potential,” and other similar terms, and future or conditional tense verbs like “could,” “may,” “might,” “see,” “should,” “will” and “would.” You can also identify forward-looking statements by the fact that they do not relate strictly to historical or current facts. For example, we may use forward-looking statements when addressing topics such as: the impact of general economic conditions, including significant inflation, interest rates and market uncertainty; the effects of geopolitical volatility, including repercussions from the wars in Ukraine and the Middle East; market and industry conditions, including competitive and pricing trends; acquisition strategy including the expected size of our acquisition program; the expected impact of acquisitions and dispositions and integrating recent acquisitions, including comments regarding the expected benefits of our acquisition of the Willis Towers Watson plc treaty reinsurance brokerage operations (which we refer to as Willis Re), BCHR Holdings, L.P., and its subsidiaries, dba Buck (which we refer to as Buck), Cadence Insurance, Inc. (which we refer to as Cadence Insurance), Eastern Insurance Group, LLC (which we refer to as Eastern Insurance), My Plan Manager Group Pty Ltd (which we refer to as My Plan Manager), and other acquisitions larger than our typical tuck-in acquisitions and the expected duration and costs of integrating such large acquisitions; the development and performance of our services and products; changes in the composition or level of our revenues or earnings; our cost structure and the size and outcome of cost-saving or restructuring initiatives; future capital expenditures; future debt levels and anticipated actions to be taken in connection with maturing debt; future debt to earnings ratios; the outcome of contingencies; dividend policy; pension obligations; cash flow and liquidity; capital structure and financial losses; future actions by regulators; the outcome of existing regulatory actions, audits, reviews or litigation; the impact of changes in accounting rules; financial markets; interest rates; foreign exchange rates; matters relating to our operations; income taxes; expectations regarding our investments; human capital management, including diversity and inclusion initiatives, and environmental, social and governance matters, including climate-resilience and climate-advising products and services and carbon emissions. These forward-looking statements are subject to certain risks and uncertainties that could cause actual results to differ materially from either historical or anticipated results depending on a variety of factors.

Potential factors that could impact results include:

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Forward-looking statements are not guarantees of future performance. They involve risks, uncertainties and assumptions, including the risk factors referred to above. Our future performance and actual results or outcomes may differ materially from those expressed in forward-looking statements. Accordingly, you should not place

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undue reliance on forward-looking statements, which speak only as of, and are based on information available to us on, the date of the applicable document. Many of the factors that will determine these results are beyond our ability to control or predict. All subsequent written and oral forward-looking statements attributable to us or any person acting on our behalf are expressly qualified in their entirety by the cautionary statements contained or referred to in this section. Forward-looking statements speak only as of the date that they are made, and we do not undertake any obligation to update any such statements or release publicly any revisions to these forward-looking statements to reflect events or circumstances after the date of this prospectus or to reflect new information, future or unexpected events or otherwise, except as required by applicable law or regulation. In addition, historical, current and forward-looking sustainability-related or ESG-related statements may be based on standards for measuring progress that are still developing, internal controls and processes that continue to evolve, and assumptions that are subject to change in the future.

A detailed discussion of the factors that could cause actual results to differ materially from our published expectations is contained under the heading “Risk Factors” in our filings with the SEC, including our Annual Report on Form 10-K for the fiscal year ended December 31, 2023, and any reports we file with the SEC in the future, which are incorporated by reference into this prospectus.

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USE OF PROCEEDS

Unless otherwise specified in a prospectus supplement accompanying this prospectus, the net proceeds from the sale of the securities to which this prospectus relates will be used for general corporate purposes. Net proceeds may be temporarily invested prior to use. We cannot predict whether the net proceeds, if invested, will yield a favorable return. Our management will have broad discretion in the application of the net proceeds we receive from the sale of the securities offered hereby, and you will be relying on the judgment of our management regarding the application of the net proceeds. We will not receive any proceeds from the sale of securities offered for sale in connection with this prospectus by selling securityholders. The selling securityholders will receive all of the net proceeds from those sales.

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SELLING SECURITYHOLDERS

Information about selling securityholders, where applicable, will be set forth in a prospectus supplement, in a post-effective amendment, or in filings we make with the SEC under the Exchange Act, which are incorporated by reference herein.

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DESCRIPTION OF SECURITIES

We will set forth in the applicable prospectus supplement a description of the debt securities, guarantees, common stock, preferred stock, warrants, depositary shares, purchase contracts, or units that may be offered under this prospectus.

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PLAN OF DISTRIBUTION

We, or any selling securityholders, may offer and sell these securities to or through one or more underwriters, dealers and agents, or directly to purchasers, or a combination thereof, on a continuous or delayed basis. We will provide the specific plan of distribution for any securities to be offered in the applicable prospectus supplement.

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LEGAL MATTERS

Gibson, Dunn & Crutcher LLP will pass upon the validity of the securities being offered by this prospectus. Any underwriters, dealers or agents will be represented by Cleary Gottlieb Steen & Hamilton LLP, New York, New York or by other legal counsel named in the applicable prospectus supplement.

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EXPERTS

The consolidated financial statements and related financial statement schedule of Arthur J. Gallagher & Co. appearing in Arthur J. Gallagher & Co.’s Annual Report (Form 10-K) for the year ended December 31, 2023, and the effectiveness of Arthur J. Gallagher & Co.’s internal control over financial reporting as of December 31, 2023, have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their reports thereon included therein, and incorporated herein by reference. Such consolidated financial statements and related financial statement schedule are incorporated herein by reference in reliance upon such reports given on the authority of such firm as experts in accounting and auditing.

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WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and current reports, proxy statements and other information with the SEC under the Exchange Act. You may access and read our SEC filings, including the complete registration statement of which this prospectus is a part and all of the exhibits to it, through commercial document retrieval services, which are available to the public, and also on the SEC’s website located at http://www.sec.gov. This site contains reports and other information that we file electronically with the SEC.

We have filed a registration statement, of which this prospectus is a part, and related exhibits with the SEC under the Securities Act. This prospectus, filed as part of the registration statement, does not contain all of the information set forth in the registration statement and its exhibits and schedules, portions of which have been omitted as permitted by the rules and regulations of the SEC. For further information about us and our securities, we refer you to the registration statement and its exhibits and schedules.

Statements in this prospectus about the contents of any contract, agreement or other documents are not necessarily complete and, in each instance, we refer you to the copy of such contract, agreement or document filed as an exhibit to the registration statement, with each such statement being qualified in all respects by reference to the document to which it refers.

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INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

We incorporate information into this prospectus by reference, which means that we can disclose important information to you by referring you to those documents, which have been separately filed with the SEC. The information incorporated by reference is considered to be part of this prospectus, and information that we file later with the SEC will automatically update and supersede this information. We are incorporating by reference our filings listed below and any additional documents that we may file with the SEC pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act on or after the date of this prospectus and before the termination of the offering of the securities made under this prospectus; except we are not incorporating by reference any information, documents or portions of any documents that are not deemed “filed” with the SEC, including any information furnished under Item 2.02 or Item 7.01 of any Current Report on Form 8-K or corresponding information furnished under Item 9.01 of Form 8-K (or included as an exhibit) in any past or future current report on Form 8-K that we may file with the SEC, unless specifically noted below:

Information in this prospectus supersedes related information in the documents listed above and information in subsequently filed documents supersedes related information in both this prospectus and the incorporated documents.

You may request orally or in writing, and we will provide you with, a copy of these filings, at no cost, by calling us at (630) 773-3800 or by writing to us at the following address:

General Counsel

Arthur J. Gallagher & Co.

2850 Golf Road

Rolling Meadows, Illinois 60008-4050

These filings and reports can also be found on our investor relations website, located at https://investor.ajg.com. Additionally, you may obtain copies of any of these through the SEC’s website: http://www.sec.gov.

The information contained on our website does not constitute a part of this prospectus.

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PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

Item 14. Other Expenses of Issuance and Distribution.

The expenses (other than underwriting compensation) to be incurred by us in connection with the issuance and distribution of our securities being registered hereby are:

Item 15. Indemnification of Directors and Officers.

Gallagher 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, but in view of all circumstances of the case, 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.

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Section 145 of the DGCL further provides that to the extent a director or officer of a corporation has been successful in the defense of any action, suit or proceeding referred to in subsections (a) and (b) of Section 145 of the DGCL 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 of the DGCL 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 of the DGCL.

Section 102(b)(7) of the DGCL provides that a corporation’s certificate of incorporation may provide a provision that eliminates or limits the personal liability of a director to the corporation or its stockholders for monetary damages for breach of fiduciary duty as a director, provided that such provisions shall not eliminate or limit the liability of a director (1) for any breach of the director’s duty of loyalty to the corporation or its stockholders; (2) for acts or omissions not in good faith or that involve intentional misconduct or a knowing violation of law; (3) under Section 174 of the DGCL; or (4) for any transaction from which the director derived an improper personal benefit. 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 Gallagher’s Amended and Restated By-laws provide for the indemnification of each of Gallagher’s directors, officers, employees or agents to the full extent permitted by applicable law, including, without limitation, the DGCL.

Article Seven of Gallagher’s Amended and Restated By-laws provides that Gallagher 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 Gallagher’s directors, officers, employees or agents, or is or was serving at Gallagher’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 Gallagher’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 Gallagher or in Gallagher’s right, and provided further that such person shall not have been adjudged liable to Gallagher, 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 Twelve of Gallagher’s Restated Certificate of Incorporation eliminates the liability of Gallagher’s directors or officers for monetary damages for breach of fiduciary duty as a director or officer except to the extent such exemption from liability or limitation is not permitted by the DGCL. It further provides that any amendment, modification or repeal of the foregoing sentence will not adversely affect any right or protection of any of Gallagher’s directors or officers in respect of any act or omission occurring prior to the time of such amendment, modification or repeal.

Gallagher 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 and/or the Securities Exchange Act.

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

Item 16. Exhibits

The following exhibits are filed herewith or incorporated herein by reference.

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Item 17. Undertakings.

The undersigned registrant hereby undertakes:

provided, however, that paragraphs (1), (2) and (3) above 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 Commission 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, or is contained in a form of prospectus filed pursuant to Rule 424(b) that is part of the registration statement.

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SIGNATURES

Pursuant to the requirements of the Securities Act, the registrant 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 the 12th day of February, 2024.

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POWER OF ATTORNEY

We, the undersigned directors and officers, do hereby constitute and appoint Walter D. Bay and Douglas K. Howell, and each of them severally, our true and lawful attorneys-in-fact and agents with full power of substitution and re-substitution for us and in our name, place, and stead, 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, and any rules, regulations and requirements of the Securities and Exchange Commission, in connection with this registration statement on Form S-3, 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 to file the same, with all exhibits thereto, and other documents in connection therewith; 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.

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Exhibit 5.1

February 12, 2024

Arthur J. Gallagher & Co.

2850 Golf Road

Rolling Meadows, Illinois 60008

Re: Arthur J. Gallagher & Co.

Registration Statement on Form S-3

Ladies and Gentlemen:

We have acted as counsel to Arthur J. Gallagher & Co., a Delaware corporation (the “Company”), in connection with the preparation and filing with the Securities and Exchange Commission (the “Commission”) of a Registration Statement on Form S-3 (the “Registration Statement”) under the Securities Act of 1933, as amended (the “Securities Act”), relating to the registration under the Securities Act and the proposed issuance and sale from time to time pursuant to Rule 415 under the Securities Act, together or separately and in one or more series (if applicable) of:

(i) the Company’s unsecured debt securities (the “Debt Securities”);

(ii) guarantees by the Company of debt securities (the “Guarantees”);

(iii) shares of the Company’s common stock, par value $1.00 per share (the “Common Stock”);

(iv) shares of the Company’s preferred stock, no par value (the “Preferred Stock”);

(v) warrants for the purchase of Common Stock, Preferred Stock, Depositary Shares or Debt Securities (the “Warrants”);

(vi) depositary shares each representing a fraction of a share of a particular series of Preferred Stock (the “Depositary Shares”);

(vii) contracts for the purchase or sale of Debt Securities, Preferred Stock or Common Stock or other securities, currencies or commodities (the “Purchase Contracts”); and

(viii) units of the Company comprised of any combination of Common Stock, Preferred Stock, Depositary Shares, Purchase Contracts or Debt Securities (the “Units”).

The Debt Securities, Guarantees, Common Stock, Preferred Stock, Warrants, Depositary Shares, Purchase Contracts and Units are collectively referred to herein as the “Securities.” The Debt Securities are to be issued under an indenture entered into between the Company and The Bank of New York Mellon Trust Company, N.A. (the “Trust Company”), as indenture trustee (the “Base Indenture”).

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In arriving at the opinions 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 form of the Base Indenture and such other documents, corporate records, certificates of officers of the Company and of public officials and other instruments as we have deemed necessary or advisable to enable us to render these opinions. In our examination, we have assumed 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. As to any facts material to these opinions, we have relied to the extent we deemed appropriate and without independent investigation upon statements and representations of officers and other representatives of the Company and others.

We have assumed without independent investigation that:

(i) at the time any Securities are sold pursuant to the Registration Statement (the “Relevant Time”), the Registration Statement and any supplements and amendments thereto (including post-effective amendments) will be effective and will comply with all applicable laws;

(ii) at the Relevant Time, a prospectus supplement will have been prepared and filed with the Commission describing the Securities offered thereby and all related documentation and will comply with all applicable laws;

(iii) all Securities will be issued and sold in the manner stated in the Registration Statement and the applicable prospectus supplement;

(iv) at the Relevant Time, all corporate or other action required to be taken by the Company to duly authorize each proposed issuance of Securities and any related documentation (including (i) the due reservation of any shares of Common Stock or Preferred Stock for issuance upon exercise, conversion or exchange of any Securities for Common Stock or Preferred Stock (a “Convertible Security”), and (ii) the execution (in the case of certificated Securities), delivery and performance of the Securities and any related documentation referred to in paragraphs 1 through 8 below) shall have been duly completed and shall remain in full force and effect;

(v) upon issuance of any Common Stock or Preferred Stock, including upon exercise, conversion or exchange of any Convertible Security, the total number of shares of Common Stock or Preferred Stock issued and outstanding will not exceed the total number of shares of Common Stock or Preferred Stock, as applicable, that the Company is then authorized to issue under its certificate of incorporation and other relevant documents;

(vi) in the case of Debt Securities, at the Relevant Time, the Base Indenture shall have been duly executed and delivered by the Company and all other parties thereto and duly qualified under the Trust Indenture Act of 1939, as amended; and

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(vii) at the Relevant Time, a definitive purchase, underwriting or similar agreement and any other necessary agreement with respect to any Securities offered or issued will have been duly authorized by all necessary corporate or other action of the Company and duly executed and delivered by the Company and the other parties thereto.

Based on the foregoing and in reliance thereon, and subject to the assumptions, exceptions, qualifications and limitations set forth herein, we are of the opinion that:

1. With respect to any Debt Securities, when:

such Debt Securities will be legal, valid and binding obligations of the Company, enforceable against the Company in accordance with their terms.

2. With respect to any Guarantees, when:

such Guarantees will be legal, valid and binding obligations of the Company, enforceable against the Company in accordance with their terms.

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3. With respect to shares of Common Stock, when:

such shares of Common Stock will be validly issued, fully paid and non-assessable.

4. With respect to any shares of Preferred Stock, when:

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such shares of Preferred Stock will be validly issued, fully paid and non-assessable.

5. With respect to any Warrants, when:

such Warrants will be legal, valid and binding obligations of the Company, enforceable against the Company in accordance with their terms.

6. With respect to Depositary Shares, when:

the depositary receipts evidencing the Depositary Shares will be legal, valid and binding obligations of the Company, enforceable against the Company in accordance with their terms.

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7. With respect to any Purchase Contracts, when:

such Purchase Contracts will be legal, valid and binding obligations of the Company, enforceable in accordance with their terms.

8. With respect to any Units, when:

the Units will be legal, valid and binding obligations of the Company, enforceable against the Company in accordance with their terms.

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The opinions expressed above are subject to the following exceptions, qualifications, limitations and assumptions:

A. We render no opinion herein as to matters involving the laws of any jurisdiction other than the State of New York and the United States of America and, for purposes of paragraphs 3 and 4 above, the Delaware General Corporation Law. We are not admitted to practice in the State of Delaware; however, we are generally familiar with the Delaware General Corporation Law as currently in effect and have made such inquiries as we consider necessary to render the opinions contained in paragraphs 3 and 4 above. This opinion is limited to the effect of the current state of the laws of the State of New York, the United States of America and, to the limited extent set forth above, the laws of the State of Delaware and 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.

B. The opinions above with respect to the Indenture, the Debt Securities, the Guarantees, the Guarantee Agreement, the depositary receipts representing the Depositary Shares, the Deposit Agreement, the Purchase Contracts, any Purchase Contract Agreement, the Warrants, the Warrant Agreement, the Units and the Unit Agreement (collectively, the “Documents”) are each subject to (i) the effect of any bankruptcy, insolvency, reorganization, moratorium, arrangement or similar laws affecting the rights and remedies of creditors generally, including without limitation the effect of statutory or other laws regarding fraudulent transfers or preferential transfers, (ii) general principles of equity, including without limitation concepts of materiality, reasonableness, good faith and fair dealing and the possible unavailability of specific performance, injunctive relief or other equitable remedies regardless of whether enforceability is considered in a proceeding in equity or at law and (iii) the provisions of Article 7 of the Certificate of Incorporation of the Company.

C. We express no opinion regarding the effectiveness of (i) any waiver of stay, extension or usury laws; (ii) provisions relating to indemnification, exculpation or contribution, to the extent such provisions may be held unenforceable as contrary to public policy or federal or state securities laws or due to the negligence or willful misconduct of the indemnified party; (iii) any purported fraudulent transfer “savings” clause; (iv) any provision in any Document waiving the right to object to venue in any court; (v) any agreement to submit to the jurisdiction of any Federal court; (vi) any waiver of the right to jury trial or (vii) any provision to the effect that every right or remedy is cumulative and may be exercised in addition to any other right or remedy or that the election of some particular remedy does not preclude recourse to one or more others.

D. To the extent relevant to our opinions in paragraphs 5, 6, 7 and 8 and not covered by our opinions in paragraphs 1, 2, 3 or 4, we have assumed that any securities, currencies or commodities underlying, comprising or issuable upon exchange, conversion or exercise of any Warrants, Depositary Shares, Purchase Contracts or Units are validly issued, fully paid and non-assessable (in the case of an equity security) or a legal, valid and binding obligation of the issuer thereof, enforceable against such issuer in accordance with its terms.

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You have informed us that you intend to issue Securities from time to time on a delayed or continuous basis, and we understand that prior to issuing any Securities pursuant to the Registration Statement (i) you will advise us in writing of the terms thereof, and (ii) you will afford us an opportunity to (x) review the operative documents pursuant to which such Securities are to be issued or sold (including the applicable offering documents), and (y) file such supplement or amendment to this opinion (if any) as we may reasonably consider necessary or appropriate.

We consent to the filing of this opinion as an exhibit to the Registration Statement, and we further consent to the use of our name under the caption “Legal Matters” in the Registration Statement and the prospectus that forms a part thereof. 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 promulgated thereunder.

Exhibit 23.2

Consent of Independent Registered Public Accounting Firm

We consent to the reference to our firm under the caption “Experts” in this Registration Statement (Form S-3) and related Prospectus of Arthur J. Gallagher & Co. for the registration of debt securities, guarantees, common stock, preferred stock, warrants, depository shares, purchase contracts, and units and to the incorporation by reference therein of our reports dated February 9, 2024, with respect to the consolidated financial statements and related financial statement schedule 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, 2023, filed with the Securities and Exchange Commission.

1

Exhibit 25.1

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM T-1

STATEMENT OF ELIGIBILITY

UNDER THE TRUST INDENTURE ACT OF 1939

OF A CORPORATION DESIGNATED TO ACT AS TRUSTEE

THE BANK OF NEW YORK MELLON TRUST COMPANY, N.A.

(Exact name of trustee as specified in its charter)

ARTHUR J. GALLAGHER & CO.

(Exact name of obligor as specified in its charter)

Debt Securities

(Title of the indenture securities)

Yes.

If the obligor is an affiliate of the trustee, describe each such affiliation.

None.

Exhibits identified in parentheses below, on file with the Commission, are incorporated herein by reference as an exhibit hereto, pursuant to Rule 7a-29 under the Trust Indenture Act of 1939 (the “Act”).

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SIGNATURE

Pursuant to the requirements of the Act, the trustee, The Bank of New York Mellon Trust Company, N.A., a banking association organized and existing under the laws of the United States of America, has duly caused this statement of eligibility to be signed on its behalf by the undersigned, thereunto duly authorized, all in the City of Houston, and State of Texas, on the 29th day of January, 2024.

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EXHIBIT 7

Consolidated Report of Condition of

THE BANK OF NEW YORK MELLON TRUST COMPANY, N.A.

of 333 South Hope Street, Suite 2525, Los Angeles, CA 90071

At the close of business September 30, 2023, published in accordance with Federal regulatory authority instructions.

I, Matthew J. McNulty, CFO of the above-named bank do hereby declare that the Reports of Condition and Income (including the supporting schedules) for this report date have been prepared in conformance with the instructions issued by the appropriate Federal regulatory authority and are true to the best of my knowledge and belief.

We, the undersigned directors (trustees), attest to the correctness of the Report of Condition (including the supporting schedules) for this report date and declare that it has been examined by us and to the best of our knowledge and belief has been prepared in conformance with the instructions issued by the appropriate Federal regulatory authority and is true and correct.

Exhibit 107

Calculation of Filing Fee Tables

Form S-3

(Form Type)

Arthur J. Gallagher & Co. (Registrant)

(Exact Name of Registrant as Specified in its Charter)

Table 1: Newly Registered and Carry Forward Securities