PIONEER MUNICIPAL HIGH INCOME FUND, INC.

ARTICLES OF INCORPORATION

ARTICLE I

INCORPORATOR

The undersigned, Hirsh Ament, whose address is c/o Venable LLP, 750 E. Pratt Street, Suite 900, Baltimore, MD 21202, being at least 18 years of age, does hereby form a corporation under the general laws of the State of Maryland.

ARTICLE II

NAME

The name of the corporation (the “Corporation”) is:

Pioneer Municipal High Income Fund, Inc.

ARTICLE III

PURPOSE

The purposes for which the Corporation is formed are to conduct and carry on the business of a closed-end management investment company registered under the Investment Company Act of 1940, as amended (the “1940 Act”), and to engage in any lawful act or activity for which corporations may be organized under the general laws of the State of Maryland as now or hereafter in force.

ARTICLE IV

PRINCIPAL OFFICE IN STATE AND RESIDENT AGENT

The address of the principal office of the Corporation in the State of Maryland is c/o CSC-Lawyers Incorporating Service Company, 7 St. Paul Street, Suite 820, Baltimore, Maryland 21202. The name and address of the resident agent of the Corporation in the State of Maryland are CSC-Lawyers Incorporating Service Company, 7 St. Paul Street, Suite 820, Baltimore, Maryland 21202. The resident agent is a Maryland corporation.

ARTICLE V

PROVISIONS FOR DEFINING, LIMITING

AND REGULATING CERTAIN POWERS OF THE

CORPORATION AND OF THE STOCKHOLDERS AND DIRECTORS

Section 5.1 Number, Vacancies, Classification and Election of Directors. The business and affairs of the Corporation shall be managed under the direction of the Board of

Directors. The number of directors of the Corporation initially shall be one, which number may be increased or decreased only by the Board of Directors pursuant to the Bylaws of the Corporation (the “Bylaws”), but shall never be less than the minimum number required by the Maryland General Corporation Law (the “MGCL”). Each director shall have the qualifications, if any, specified in the Bylaws.

Any vacancy on the Board of Directors may be filled in the manner provided in the Bylaws. The Corporation elects, effective at such time as it becomes eligible under Section 3-802 of the MGCL to make the election provided for under Section 3-804(c) of the MGCL, that, except as may be provided by the Board of Directors in setting the terms of any class or series of Preferred Stock (as defined below) or as may be required by the 1940 Act, any and all vacancies on the Board of Directors may be filled only by the affirmative vote of a majority of the directors remaining in office, even if the remaining directors do not constitute a quorum, and any director elected to fill a vacancy shall serve for the remainder of the full term of the directorship in which such vacancy occurred and until a successor is duly elected and qualifies. The name of the director who shall serve until his successor is duly elected and qualifies is Christopher Kelley.

On the first date on which the Corporation has more than one stockholder of record, the directors (other than any director elected solely by holders of one or more classes or series of Preferred Stock in connection with dividend arrearages) shall be classified, with respect to the terms for which they severally hold office, into three classes as determined by the Board of Directors, with a class of directors to hold office initially for a term expiring at the first annual meeting of stockholders subsequent to their election, a class of directors to hold office initially for a term expiring at the second annual meeting of stockholders subsequent to their election, and a class of directors to hold office initially for a term expiring at the third annual meeting of stockholders subsequent to their election, with each director to hold office until her or his successor is duly elected and qualifies. At each annual meeting of the stockholders, commencing with the first annual meeting of stockholders subsequent to the classification of directors, the successors to the class of directors whose term expires at such meeting shall be elected to hold office for a term expiring at the third succeeding annual meeting of stockholders following the meeting at which they were elected and until their successors are duly elected and qualify.

Except as otherwise provided in the Bylaws, each director shall be elected by the affirmative vote of the stockholders entitled to cast a majority of the votes entitled to be cast in the election of directors.

Section 5.2 Extraordinary Actions. Except as specifically provided in Section 5.6 (relating to removal of directors), and in Section 7.2 (relating to certain actions and certain amendments to the charter of the Corporation (the “Charter”)), notwithstanding any provision of law requiring any action to be taken or approved by the affirmative vote of the stockholders entitled to cast a greater number of votes, any such action shall be effective and valid if declared advisable by the Board of Directors and taken or approved by the affirmative vote of stockholders entitled to cast a majority of all the votes entitled to be cast on the matter.

Section 5.3 Authorization by Board of Stock Issuance. The Board of Directors may authorize the issuance from time to time of shares of stock of the Corporation of any class or series, whether now or hereafter authorized, or securities or rights convertible into shares of its

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stock of any class or series, whether now or hereafter authorized, for such consideration, if any, as the Board of Directors may deem advisable (or without consideration in the case of a stock split or stock dividend), subject to such restrictions or limitations, if any, as may be set forth in the Charter or the Bylaws.

Section 5.4 Preemptive Rights and Appraisal Rights. Except as may be provided by the Board of Directors in setting the terms of classified or reclassified shares of stock pursuant to Section 6.4 or as may otherwise be provided by a contract approved by the Board of Directors, no holder of shares of stock of the Corporation shall, as such holder, have any preemptive right to purchase or subscribe for any additional shares of stock of the Corporation or any other security of the Corporation which it may issue or sell. Holders of shares of stock of the Corporation shall not be entitled to exercise any rights of an objecting stockholder provided for under Title 3, Subtitle 2 of the MGCL or any successor statute unless the Board of Directors, upon such terms and conditions as specified by the Board of Directors, shall determine that such rights apply, with respect to all or any shares of all or any classes or series of stock, to one or more transactions occurring after the date of such determination in connection with which holders of such shares would otherwise be entitled to exercise such rights.

Section 5.5 Determinations by Board. The determination as to any of the following matters, made by or pursuant to the direction of the Board of Directors, shall be final and conclusive and shall be binding upon the Corporation and every holder of shares of its stock: the amount of the net income of the Corporation for any period and the amount of assets at any time legally available for the payment of dividends, acquisition of its stock or the payment of other distributions on its stock; the amount of paid-in surplus, net assets, other surplus, cash flow, net profit, net assets in excess of capital, undivided profits or excess of profits over losses on sales of assets; the amount, purpose, time of creation, increase or decrease, alteration or cancellation of any reserves or charges and the propriety thereof (whether or not any obligation or liability for which such reserves or charges shall have been created shall have been paid or discharged); any interpretation or resolution of any ambiguity with respect to any provision of the Charter (including any of the terms, preferences, conversion or other rights, voting powers or rights, restrictions, limitations as to dividends or other distributions, qualifications or terms or conditions of redemption of any shares of any class or series of stock of the Corporation) or of the Bylaws; the fair value, or any sale, bid or asked price to be applied in determining the fair value, of any asset owned or held by the Corporation or of any shares of stock of the Corporation; the number of shares of stock of any class or series of the Corporation; any matter relating to the acquisition, holding and disposition of any assets by the Corporation; any interpretation of the terms and conditions of one or more agreements with any person, corporation, association, company, trust, partnership (limited or general) or other organization; the compensation of directors, officers, employees or agents of the Corporation; or any other matter relating to the business and affairs of the Corporation or required or permitted by applicable law, the Charter or Bylaws or otherwise to be determined by the Board of Directors.

Section 5.6 Removal of Directors. Subject to the rights of holders of one or more classes or series of Preferred Stock to elect or remove one or more directors, any director, or the entire Board of Directors, may be removed from office at any time, but only for cause and then only by the affirmative vote of at least three-quarters of the votes entitled to be cast generally in the election of directors. For the purpose of this paragraph, “cause” shall mean, with respect to any particular director, conviction of a felony or a final judgment of a court of competent jurisdiction holding that such director caused demonstrable, material harm to the Corporation through bad faith or active and deliberate dishonesty.

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Section 5.7 Corporate Opportunities. The Corporation shall have the power, by resolution of the Board of Directors, to renounce any interest or expectancy of the Corporation in, or in being offered an opportunity to participate in, business opportunities or classes or categories of business opportunities that are presented to the Corporation or developed by or presented to one or more directors or officers of the Corporation.

ARTICLE VI

STOCK

Section 6.1 Authorized Shares. The Corporation has authority to issue 1,100,000,000 shares of stock, initially consisting of 1,000,000,000 shares of common stock, $0.001 par value per share (“Common Stock”), and 100,000,000 shares of Preferred Stock, $0.001 par value per share (“Preferred Stock”). The aggregate par value of all authorized shares of stock having par value is $1,100,000. If shares of one class or series of stock are classified or reclassified into shares of another class or series of stock pursuant to this Article VI, the number of authorized shares of the former class or series shall be automatically decreased and the number of shares of the latter class or series shall be automatically increased, in each case by the number of shares so classified or reclassified, so that the aggregate number of shares of stock of all classes and series that the Corporation has authority to issue shall not be more than the total number of shares of stock set forth in the first sentence of this paragraph. The Board of Directors, with the approval of a majority of the entire Board of Directors and without any action by the stockholders of the Corporation, may amend the Charter from time to time to increase or decrease the aggregate number of shares of stock or the number of shares of stock of any class or series that the Corporation has authority to issue.

Section 6.2 Common Stock. Each share of Common Stock shall entitle the holder thereof to one vote. The Board of Directors may reclassify any unissued shares of Common Stock from time to time in one or more classes or series of stock.

Section 6.3 Preferred Stock. The Board of Directors may classify any unissued shares of Preferred Stock and reclassify any previously classified but unissued shares of Preferred Stock.

Section 6.4 Classified or Reclassified Shares. Prior to issuance of classified or reclassified shares of any class or series, the Board of Directors by resolution shall: (a) designate that class or series to distinguish it from all other classes and series of stock of the Corporation; (b) specify the number of shares to be included in the class or series; (c) set or change, subject to the express terms of any class or series of stock of the Corporation outstanding at the time, the preferences, conversion or other rights, voting powers (including exclusive voting rights, if any), restrictions, limitations as to dividends or other distributions, qualifications and terms and conditions of redemption for each class or series; and (d) cause the Corporation to file articles supplementary with the State Department of Assessments and Taxation of Maryland. Any of the terms of any class or series of stock set or changed pursuant to clause (c) of this Section 6.4 may

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be made dependent upon facts or events ascertainable outside the Charter (including determinations by the Board of Directors or other facts or events within the control of the Corporation) and may vary among holders thereof, provided that the manner in which such facts, events or variations shall operate upon the terms of such class or series of stock is clearly and expressly set forth in the articles supplementary or other Charter document.

Section 6.5 Inspection of Books and Records. A stockholder that is otherwise eligible under applicable law to inspect the Corporation’s books of account, stock ledger, or other specified documents of the Corporation shall have no right to make such inspection if the Board of Directors, in its sole discretion determines that such stockholder has an improper purpose for requesting such inspection.

Section 6.6 Charter and Bylaws. The rights of all stockholders and the terms of all stock of the Corporation are subject to the provisions of the Charter and the Bylaws. The Board of Directors shall have the exclusive power to make, alter, amend or repeal the Bylaws.

Section 6.7 Special Meetings of Stockholders. A special meeting of stockholders requested by the stockholders may only be called upon the request of stockholders entitled to cast not less than a majority of all the votes entitled to be cast on such matter at such meeting in accordance with the Bylaws.

ARTICLE VII

AMENDMENTS; CERTAIN EXTRAORDINARY TRANSACTIONS

Section 7.1 Amendments Generally. The Corporation reserves the right from time to time to make any amendment to the Charter, now or hereafter authorized by law, including any amendment altering the terms or contract rights, as expressly set forth in the Charter, of any shares of outstanding stock. All rights and powers conferred by the Charter on stockholders, directors and officers are granted subject to this reservation.

Section 7.2. Approval of Certain Extraordinary Actions and Charter Amendments.

(a) Required Votes. The affirmative vote of the holders of shares entitled to cast at least three-quarters of the votes entitled to be cast on the matter, each voting as a separate class (except as provided with respect to a particular class or series of stock, when required by the 1940 Act to be voted in the aggregate and not by individual class or series), shall be necessary to effect:

(i) Any amendment to the Charter to make the Common Stock a “redeemable security” or any other proposal to convert the Corporation, whether by merger or otherwise, from a “closed-end company” to an “open-end company” (as such terms are defined in the 1940 Act);

(ii) The liquidation or dissolution of the Corporation and any amendment to the Charter to effect any such liquidation or dissolution;

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(iii) Any amendment to, or any amendment inconsistent with, the provisions of Section 5.1, Section 5.2, Section 5.6, Section 6.6, Section 7.1 or this Section 7.2;

(iv) Any merger, conversion, consolidation, share exchange or sale or exchange of all or substantially all of the assets of the Corporation that the MGCL requires be approved by the stockholders of the Corporation; and

(v) Any transaction between the Corporation and a person, or group of persons acting together (including, without limitation, a “group” for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, or any successor provision), that is entitled to exercise or direct the exercise, or acquire the right to exercise or direct the exercise, directly or indirectly, other than solely by virtue of a revocable proxy, of one-tenth or more of the voting power in the election of directors generally, or any person controlling, controlled by or under common control with any such person or member of such group;

provided, however, that, if the Continuing Directors (as defined herein), by a vote of at least three-quarters of such Continuing Directors, in addition to approval by the Board of Directors, approve such proposal, transaction or amendment, the affirmative vote of the holders of a majority of the votes entitled to be cast shall be sufficient to approve such proposal, transaction or amendment; and provided further, that, with respect to any proposal, transaction or amendment referred to in (v) above, if such proposal, transaction or amendment is approved by the Continuing Directors, by a vote of at least three-quarters of such Continuing Directors, no stockholder approval of such proposal, transaction or amendment shall be required unless the MGCL or another provision of the Charter or Bylaws otherwise requires such approval.

(b) Continuing Directors. “Continuing Directors” means (i) the named directors identified in Section 5.1, (ii) the directors whose nomination for election by the stockholders or whose election by the Board of Directors to fill vacancies on the Board is approved by a majority of the directors identified in Section 5.1, who are on the Board at the time of the nomination or election, as applicable, or (iii) any successor directors whose nomination for election by the stockholders or whose election by the Board of Directors to fill vacancies is approved by a majority of the Continuing Directors or successor Continuing Directors, who are on the Board at the time of the nomination or election, as applicable.

ARTICLE VIII

LIMITATION OF LIABILITY; INDEMNIFICATION

AND ADVANCE OF EXPENSES

Section 8.1 Limitation of Liability. To the maximum extent that Maryland law in effect from time to time permits limitation of the liability of directors and officers of a corporation, no present or former director or officer of the Corporation shall be liable to the Corporation or its stockholders for money damages.

Section 8.2 Indemnification and Advance of Expenses. To the maximum extent permitted by Maryland law in effect from time to time, the Corporation shall indemnify and, without requiring a preliminary determination of the ultimate entitlement to

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indemnification, shall pay or reimburse reasonable expenses in advance of final disposition of a proceeding to (a) any individual who is a present or former director or officer of the Corporation and who is made or threatened to be made a party to, or witness in, the proceeding by reason of his or her service in that capacity and (b) any individual who, while a director or officer of the Corporation and at the request of the Corporation, serves or has served as a director, officer, partner, member, manager, trustee, employee or agent of another corporation, real estate investment trust, partnership, limited liability company, joint venture, trust, employee benefit plan or other enterprise and who is made or threatened to be made a party to, or witness in, the proceeding by reason of his or her service in that capacity, in either case, from and against any claim or liability to which such person may become subject or which such person may incur by reason of his or her service in such capacity. The rights to indemnification and advance of expenses provided by the Charter shall vest immediately upon election of a director or officer. The Corporation may, with the approval of the Board of Directors, provide such indemnification and advance of expenses to an individual who served a predecessor of the Corporation in any of the capacities described in (a) or (b) above and to any employee or agent of the Corporation or a predecessor of the Corporation. The indemnification and payment or reimbursement of expenses provided in the Charter shall not be deemed exclusive of or limit in any way other rights to which any person seeking indemnification or payment or reimbursement of expenses may be or may become entitled under any bylaw, resolution, insurance, agreement or otherwise.

Section 8.3 1940 Act. The provisions of this Article VIII shall be subject to the limitations of the 1940 Act.

Section 8.4 Amendment or Repeal. Neither the amendment nor repeal of this Article VIII, nor the adoption or amendment of any other provision of the Charter or Bylaws inconsistent with this Article VIII, shall apply to or affect in any respect the applicability of the preceding sections of this Article VIII with respect to any act or failure to act which occurred prior to such amendment, repeal or adoption.

[SIGNATURE PAGE FOLLOWS]

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IN WITNESS WHEREOF, I have signed these Articles of Incorporation and acknowledge the same to be my act on this 2^nd day of April, 2021.

/s/ Hirsh Ament

Hirsh Ament

Incorporator

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