Second Supplemental Indenture dated as of August 24, 2020, between The Hanover Insurance Group, Inc. and U.S. Bank National Association, as trustee, supplementing the Base Indenture dated as of April 8, 2016

Exhibit 4.2

THE HANOVER INSURANCE GROUP, INC.,

as Issuer

and

U.S. Bank National Association,

as Trustee

SECOND SUPPLEMENTAL INDENTURE

Dated as of August 24, 2020

to the Indenture dated as of April 8, 2016

2.500% Notes due 2030

TABLE OF CONTENTS

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SECOND SUPPLEMENTAL INDENTURE

SECOND SUPPLEMENTAL INDENTURE (this “Second Supplemental Indenture”), dated as of August 24, 2020, between The Hanover Insurance Group, Inc., a Delaware corporation (the “Company”), and U.S. Bank National Association, as Trustee (the “Trustee”).

RECITALS OF THE COMPANY

WHEREAS, the Company and the Trustee executed and delivered an Indenture, dated as of April 8, 2016 (the “Base Indenture,” and together with this Second Supplemental Indenture, the “Indenture”), to provide for the issuance by the Company from time to time of Securities to be issued in one or more series as provided in the Base Indenture;

WHEREAS, Section 9.1 of the Base Indenture provides, among other things, that the Company and the Trustee may enter into indentures supplemental to the Base Indenture, without the consent of any Holders of Securities, to establish the form of any Security, as permitted by Section 2.1 of the Base Indenture, and to provide for the issuance of the Notes (as defined below), as permitted by Section 3.1 of the Base Indenture, and to set forth the terms thereof;

WHEREAS, the Company desires to execute this Second Supplemental Indenture pursuant to Section 2.1 of the Base Indenture to establish the form, and pursuant to Section 3.1 of the Base Indenture to provide for the issuance, of a series of its senior notes designated as its 2.500% Notes due 2030 (the “Notes”), in an initial aggregate principal amount of $300,000,000. The Notes are a series of securities as referred to in Section 3.1 of the Base Indenture;

WHEREAS, the Company has requested that the Trustee execute and deliver this Second Supplemental Indenture;

WHEREAS, all things necessary have been done by the Company to make this Second Supplemental Indenture, when executed and delivered by the Company, a valid supplement to the Indenture; and

WHEREAS, all things necessary have been done by the Company to make the Notes, when executed by the Company and authenticated and delivered in accordance with the provisions of the Indenture, the valid obligations of the Company;

NOW, THEREFORE, in consideration of the premises stated herein and the purchase of the Notes by the Holders thereof, the Company and the Trustee mutually covenant and agree for the equal and proportionate benefit of the respective Holders from time to time of the Notes as follows:

ARTICLE 1

APPLICATION OF SUPPLEMENTAL INDENTURE

SECTION 1.01. Application of Second Supplemental Indenture. Notwithstanding any other provision of this Second Supplemental Indenture, all provisions of this Second Supplemental Indenture are expressly and solely for the benefit of the Holders of the Notes and any such provisions shall not be deemed to apply to any other securities issued under

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the Indenture and shall not be deemed to amend, modify or supplement the Base Indenture for any purpose other than with respect to the Notes. Unless otherwise expressly specified, references in this Second Supplemental Indenture to specific Article numbers or Section numbers refer to Articles and Sections contained in this Second Supplemental Indenture as they amend or supplement the Base Indenture, and not the Base Indenture or any other document. All Initial Notes and Additional Notes, if any, shall be treated as a single class for all purposes of the Indenture, including waivers, amendments, redemptions and offers to purchase, except for Additional Notes, if any issued with a different CUSIP number.

ARTICLE 2

DEFINITIONS

SECTION 2.01. Certain Terms Defined in the Indenture. For purposes of this Second Supplemental Indenture, all capitalized terms used but not defined herein shall have the meanings ascribed to such terms in the Base Indenture, as amended hereby.

SECTION 2.02. Definitions. For the benefit of the Holders of the Notes, Section 1.1 of the Base Indenture shall be amended by adding the following new definitions:

“Additional Notes” has the meaning specified in Section 3.04(b) hereto.

“Comparable Treasury Issue” means the United States Treasury security or securities selected by an Independent Investment Banker as having an actual or interpolated maturity comparable to the remaining term of the Notes to be redeemed that would be utilized, at the time of selection and in accordance with customary financial practice, in pricing new issues of corporate debt securities of a comparable maturity to the remaining term of such Notes.

“Comparable Treasury Price” means, with respect to any Redemption Date, (A) the average of the Reference Treasury Dealer Quotations for such Redemption Date, after excluding the highest and lowest such Reference Treasury Dealer Quotations, or (B) if the Company obtains fewer than four such Reference Treasury Dealer Quotations, the average of all such quotations.

“Consolidated Assets” mean the Company’s assets and the assets of the Company’s consolidated subsidiaries, to be determined as of the last day of the most recent fiscal quarter ended at least 30 days prior to the date of the determination, for which internal financial statements are available and have been prepared in accordance with generally accepted accounting principles in the United States as in effect on the last day of that fiscal quarter.

“Global Note” has the meaning specified in Section 3.01(c) and is substantially in the form of Exhibit A.

“Independent Investment Banker” means one of the Reference Treasury Dealers appointed by the Company.

“Initial Notes” has the meaning specified in Section 3.04(b) hereto.

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“Lien” means any lien, mortgage, pledge, security interest, charge or encumbrance of any kind (including any conditional sale or other title retention agreement and any lease in the nature thereof).

“Notes” has the meaning specified in the recitals hereto.

“Preferred Stock,” as applied to the Capital Stock of any corporation, means Capital Stock of any class or classes (however designated) which is preferred as to the payment of the dividends, or as to the distribution of assets upon any voluntary or involuntary liquidation or dissolution of such corporation, over shares of Capital Stock of any other class of such corporation.

“Reference Treasury Dealer” means each of (i) Morgan Stanley & Co. LLC or its affiliates, Wells Fargo Securities, LLC or its affiliates and J.P. Morgan Securities LLC or its affiliates ; and (ii) up to three other primary U.S. Government securities dealers in the City of New York (each, a “Primary Treasury Dealer”) selected by the Company, and their respective successors; provided, however, that if any of the foregoing or their affiliates shall cease to be a Primary Treasury Dealer, the Company shall substitute therefor another such Primary Treasury Dealer.

“Reference Treasury Dealer Quotations” means, with respect to each Reference Treasury Dealer and any Redemption Date, the average, as determined by the Company, of the bid and asked prices for the Comparable Treasury Issue (expressed in each case as a percentage of its principal amount) quoted in writing to the Company by such Reference Treasury Dealer at 3:30 p.m. New York time on the third Business Day preceding such Redemption Date.

“Restricted Subsidiary” means (i) any Subsidiary the assets of which, determined as of the last day of the most recent fiscal quarter ended at least 30 days prior to the date of determination, for which internal financial statements are available and have been prepared in accordance with generally accepted accounting principles in the United States as in effect on the last day of that fiscal quarter, exceed 15% of the Consolidated Assets, or (ii) any Subsidiary designated as a Restricted Subsidiary by the board of directors, or similar governing body, of such Subsidiary, effective as of the date of such designation.

“Treasury Rate” means, with respect to any Redemption Date, the rate per annum equal to the semiannual equivalent yield to maturity or interpolated maturity (on a day count basis) of the Comparable Treasury Issue, assuming a price for the Comparable Treasury Issue (expressed as a percentage of its principal amount) equal to the Comparable Treasury Price for such Redemption Date.

ARTICLE 3

FORM AND TERMS OF THE NOTES

SECTION 3.01. Form and Dating.

(a) The Notes and the Trustee’s certificate of authentication shall be substantially in the form of Exhibit A attached hereto. The Notes shall be executed on behalf of the Company by an Officer of the Company and attested by its Secretary or one

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of its Assistant Secretaries. The Notes may have notations, legends or endorsements required by law, stock exchange rules or usage. Each Note shall be dated the date of its authentication. The Notes and any beneficial interest in the Notes shall be in minimum denominations of $2,000 and integral multiples of $1,000 in excess thereof.

(b) The terms and notations contained in the Notes shall constitute, and are hereby expressly made, a part of the Indenture, and the Company and the Trustee, by their execution and delivery of this Second Supplemental Indenture, expressly agree to such terms and provisions and to be bound thereby.

(c) The Notes shall be issued initially in the form of fully registered Global Securities (the “Global Note”), which shall be deposited on behalf of the purchasers of the Notes represented thereby with The Depository Trust Company, New York, New York (the “Depositary”) and registered in the name of Cede & Co., the Depositary’s nominee, duly executed by the Company, authenticated by the Trustee.

SECTION 3.02. Execution and Authentication. This Section 3.02 shall apply only to the Global Note deposited with or on behalf of the Depositary. The Company shall execute and the Trustee shall, in accordance with this Section 3.02, authenticate and deliver the Global Note that shall be registered in the name of the Depositary or the nominee of the Depositary and shall be delivered by the Trustee to the Depositary or pursuant to the Depositary’s instructions.

SECTION 3.03. Paying Agent. The Company initially appoints the Trustee as Paying Agent for the payment of the principal of (and premium, if any) and interest on the Notes and the office of the Trustee at U.S. Bank National Association, One Federal Street, 3^rd Floor, Boston, Massachusetts 02110, Attention: Corporate Trust Services, Reference # Hanover 2020 be and hereby is, designated as the Place of Placement where the Notes may be presented for payment.

SECTION 3.04. Terms of the Notes. The following terms relating to the Notes are hereby established:

(a) Title. The Notes shall constitute a series of Securities having the title “2.500% Notes due 2030”.

(b) Principal Amount. The aggregate principal amount of the Notes that may be initially authenticated and delivered under the Indenture (the “Initial Notes”) shall be $300,000,000 (except for Notes authenticated and delivered upon registration of, transfer of, or in exchange for, or in lieu of, other Notes pursuant to Sections 3.4, 3.5, 3.6, 9.6 or 11.7 of the Base Indenture). The Company may from time to time, without the consent of, or notice to, the Holders of Notes, issue additional Notes (in any such case “Additional Notes”) having the same ranking and the same interest rate, Maturity and other terms as the Initial Notes (other than the public offering price and date of issuance and, under certain circumstances, the date from which interest thereon will begin to accrue), provided, however, that no Additional Notes may be issued unless the Additional Notes are fungible with the Notes for U.S. federal income tax purposes or issued with a

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different CUSIP number. Any Additional Notes and the Initial Notes shall constitute a single series under the Indenture unless the Additional Notes are issued with a different CUSIP number. All references to the Notes shall include the Initial Notes and any Additional Notes unless the context otherwise requires or the Additional Notes are issued with a different CUSIP number.

(c) Maturity Date. The entire outstanding principal amount of the Notes shall be payable on September 1, 2030.

(d) Interest Rate. The rate at which the Notes shall bear interest shall be 2.500% per annum; the date from which interest shall accrue on the Notes shall be August 24, 2020, or the most recent Interest Payment Date to which interest has been paid or provided for; the Interest Payment Dates for the Notes shall be March 1 and September 1 of each year, beginning March 1, 2021; the interest so payable, and punctually paid or duly provided for, on any Interest Payment Date, will be paid, in immediately available funds, to the Persons in whose names the Note (or predecessor Note) is registered (which shall initially be the Depositary) at the close of business on the Regular Record Date for such interest, which shall be February 15 or August 15, as the case may be, next preceding such Interest Payment Date. Interest shall be computed on the basis of a 360-day year comprised of twelve 30-day months. For so long as the Notes are represented in global form by one or more Global Securities, all payments of principal (and premium, if any) and interest shall be made by wire transfer of immediately available funds to the Depositary or its nominee, as the case may be, as the registered owner of the Global Security representing such Notes. In the event that definitive Notes shall have been issued, all payments of principal (and premium, if any) and interest shall be made at the office of the Paying Agent at One Federal Street, 3rd Floor, Boston, Massachusetts 02110, Attention: Corporate Trust Services, Reference # Hanover 2020; provided, that the Company may at its option pay interest (i) by check to the registered address of each Holder of a definitive Note or (ii) by wire transfer of immediately available funds to the account of any registered Holder thereof, in each of cases (i) and (ii), if such Holder so requests in writing to the Trustee at least 15 days prior to the relevant Interest Payment Date.

(e) Sinking Fund. The Notes are not subject to any sinking fund.

SECTION 3.05. Optional Redemption.

(a) The provisions of Article 11 of the Base Indenture, as supplemented by the provisions of this Second Supplemental Indenture, shall apply to the Notes.

(b) At any time and from time to time prior to June 1, 2030, the Notes shall be redeemable as a whole or in part in integral multiples of $1,000 principal amount, at the Company’s option (an “Optional Redemption”), at a Redemption Price equal to the greater of (i) 100% of the principal amount of the Notes to be redeemed and (ii) the sum of the present values of the remaining scheduled payments of principal and interest thereon (exclusive of interest accrued and unpaid to the date of redemption and assuming the notes mature on June 1, 2030) discounted to the Redemption Date on a semiannual basis (assuming a 360-day year consisting of twelve 30-day months) at the Treasury Rate plus 30 basis points, plus, in each case, accrued and unpaid interest thereon to, but not including, the date of redemption.

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(c) At any time and from time to time on or after June 1, 2030, the Company may redeem the Notes as a whole or in part, at the Company’s option (a “Special Redemption”), at a Redemption Price equal to 100% of the principal amount of the Notes being redeemed, plus in each case accrued and unpaid interest thereon to, but not including, the date of redemption.

(d) Further installments of interest on the Notes to be redeemed that are due and payable on the Interest Payment Dates falling on or prior to the Redemption Date shall be payable on the Interest Payment Date to the registered Holders as of the close of business on the relevant Regular Record Date according to the Notes and the Indenture.

(e) Notice of any Optional Redemption or Special Redemption under this Section 3.05 will be mailed at least 10 days but not more than 60 days before the Redemption Date to each Holder of the Notes to be redeemed; provided, however, that notice of any Optional Redemption or Special Redemption may be mailed more than 60 days prior to the Redemption Date if the notice is issued in connection with a defeasance of the Notes or a satisfaction and discharge of Notes. If fewer than all of the Notes are to be redeemed, the Notes to be redeemed shall be selected by the Trustee by lot or any other such method as the Trustee deems to be fair and appropriate.

(f) Unless the Company defaults in payment of the Redemption Price, on and after the Redemption Date, interest will cease to accrue on the Notes or portions thereof called for Optional Redemption or Special Redemption, as the case may be, under this Section 3.05.

SECTION 3.06. Certain Interest Payments.

(a) Installments of interest that are due and payable on Notes to be repurchased or redeemed on a Redemption Date between a Regular Record Date and an Interest Payment Date shall be payable on the Redemption Date to the registered Holders as of the close of business on the relevant Regular Record Date according to the Notes and the Indenture.

ARTICLE 4

CERTAIN COVENANTS

The following covenants shall be applicable to the Company for so long as any of the Notes are Outstanding. Nothing in this Article will, however, affect the Company’s rights or obligations under any other provision of the Base Indenture or this Second Supplemental Indenture.

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SECTION 4.01. Restrictions on Issuance or Disposition of Stock of Restricted Subsidiaries.

(a) The Company will not, nor will it permit any Restricted Subsidiary to, issue, sell or otherwise dispose of any shares of Capital Stock (other than non-voting Preferred Stock) of any Restricted Subsidiary, except for:

(i) directors’ qualifying shares;

(ii) sales or other dispositions to the Company or to one or more Subsidiaries that are Restricted Subsidiaries or that will become Restricted Subsidiaries immediately after the sale or disposition;

(iii) the disposition of all or any part of the Capital Stock of any Restricted Subsidiary for consideration which is at least equal to the fair value of such Capital Stock as determined by the Company’s or such Restricted Subsidiary’s board of directors, as the case may be (acting in good faith), in any case in accordance with the laws of the jurisdiction of formation of such Person; provided, however, that any such Capital Stock issued, sold, granted, transferred or otherwise disposed of to any employee, officer, director, agent or consultant pursuant to any agreement, plan or arrangement approved by the board of directors of the Company or such Restricted Subsidiary, as appropriate, shall be deemed to be issued, sold or otherwise disposed of at fair value; or

(iv) any issuance, sale, assignment, transfer or other disposition made in compliance with an order of a court or regulatory authority of competent jurisdiction, other than an order issued at the request of the Company or any Restricted Subsidiary.

SECTION 4.02. Limitations on Liens.

(a) Except as provided below, neither the Company nor any Restricted Subsidiary may incur, issue, assume or guarantee any Indebtedness secured by a Lien on (A) any shares of Capital Stock issued by a Restricted Subsidiary and held directly or indirectly by the Company or another Restricted Subsidiary or (B) any Indebtedness of a Restricted Subsidiary owing to and held directly or indirectly by the Company or another Restricted Subsidiary, without effectively providing that the Notes (together with, if the Company shall so determine, any other Indebtedness which is not subordinated to the Notes) shall be secured equally and ratably with (or prior to) such Indebtedness, so long as such Indebtedness shall be so secured; provided, however, that this covenant shall not apply to Indebtedness secured by:

(i) Liens in favor of, or required by, governmental authorities, including insurance regulatory authorities;

(ii) Liens existing on the date of this Second Supplemental Indenture;

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(iii) Liens on any shares of Capital Stock or Indebtedness of any corporation (including any Subsidiary) (a) existing at the time such corporation becomes a Restricted Subsidiary or merges into or consolidates with the Company or a Restricted Subsidiary and (b) not incurred in contemplation thereof;

(iv) Liens in favor of the Company or any Restricted Subsidiary;

(v) Liens, pledges or deposits to secure statutory obligations, including Liens and deposits required or provided for under state insurance laws and similar regulatory statutes;

(vi) materialmen’s, mechanic’s, carrier’s, workmen’s, repairmen’s, or other like Liens, and pledges and deposits made in the ordinary course of business to obtain the release thereof; and

(vii) any extension, renewal or replacement as a whole or in part, of any Lien referred to in the foregoing clauses (i) to (vi) inclusive; provided, however, that (a) such extension, renewal or replacement Lien shall be limited to all or a part of the same shares of Capital Stock or the same Indebtedness that secured the Lien extended, renewed or replaced and (b) the Indebtedness secured by such Lien at such time is not so increased.

Any Lien that is granted to secure the Notes pursuant to this covenant shall be deemed automatically and unconditionally released and discharged upon the release and discharge of each of the Liens described above that triggered the obligation to secure the Notes.

ARTICLE 5

MISCELLANEOUS

SECTION 5.01. Trust Indenture Act Controls. If any provision of this Second Supplemental Indenture limits, qualifies or conflicts with another provision which is required to be included in this Second Supplemental Indenture by the TIA, the required provision shall control. If any provision of this Second Supplemental Indenture modifies or excludes any provision of the TIA which may be so modified or excluded, the latter provision shall be deemed to apply to this Second Supplemental Indenture as so modified or to be excluded, as the case may be.

SECTION 5.02. New York Law to Govern. The Second Supplemental Indenture and the Notes shall be governed by and construed in accordance with the laws of the State of New York.

SECTION 5.03. Counterparts. This Second Supplemental Indenture may be executed in any number of counterparts, each of which so executed shall be deemed to be an original, but all such counterparts shall together constitute but one and the same instrument. The parties hereto agree that the electronic signature of a party to this Second Supplemental Indenture shall be as valid as an original signature of such party and shall be effective to bind such party to this Second Supplemental Indenture. The words “execution,” “signed,” “signature,” and words of like import in this Second Supplemental Indenture or in any other certificate, agreement or

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document related to this Second Supplemental Indenture shall include images of manually executed signatures transmitted by facsimile or other electronic format (including, without limitation, “pdf”, “tif” or “jpg”) and other electronic signatures (including, without limitation, DocuSign). The use of electronic signatures and electronic records (including, without limitation, any contract or other record created, generated, sent, communicated, received, or stored by electronic means) shall be of the same legal effect, validity and enforceability as a manually executed signature or use of a paper-based recordkeeping system to the fullest extent permitted by applicable law, including the Federal Electronic Signatures in Global and National Commerce Act, the New York State Electronic Signatures and Records Act and any other applicable law, including, without limitation, any state law based on the Uniform Electronic Transactions Act or the Uniform Commercial Code. Without limiting the foregoing, the parties hereto agree that any electronically signed document (including this Second Supplemental Indenture) shall be deemed (i) to be “written” or “in writing”, (ii) to have been signed, and (iii) to constitute a record established and maintained in the ordinary course of business and an original written record when printed from electronic files. Such paper copies or “printouts”, if introduced as evidence in any judicial, arbitral, mediation or administrative proceeding, will be admissible as between the parties hereto to the same extent and under the same conditions as other original business records created and maintained in documentary form. Neither party hereto shall contest the admissibility of true and accurate copies of electronically signed documents on the basis of the best evidence rule or as not satisfying the business records exception to the hearsay rule. The Company agrees to assume all risks arising out of the use of using digital signatures and electronic methods to submit communications to the Trustee, including without limitation the risk of the Trustee acting on unauthorized instructions, and the risk of interception and misuse by third parties.

SECTION 5.04. Severability. If any provision of this Second Supplemental Indenture or the Notes shall be held to be illegal or unenforceable under applicable law, then the remaining provisions hereof shall be construed as though such invalid, illegal or unenforceable provision were not contained therein.

SECTION 5.05. Ratification. The Base Indenture, as supplemented and amended by this Second Supplemental Indenture, is in all respects ratified and confirmed. The Indenture shall be read, taken and construed as one and the same instrument. All provisions included in this Second Supplemental Indenture supersede any conflicting provisions included in the Base Indenture unless not permitted by law. The Trustee accepts the trusts created by the Indenture, and agrees to perform the same upon the terms and conditions of the Indenture.

SECTION 5.06. Effectiveness. The provisions of this Second Supplemental Indenture shall become effective as of the date hereof.

SECTION 5.07. Trustee Makes No Representation. The recitals contained herein are made by the Company and not by the Trustee, and the Trustee assumes no responsibility for the correctness thereof. The Trustee makes no representation as to the validity or sufficiency of this Second Supplemental Indenture. All rights, protections, privileges, indemnities and benefits granted or afforded to the Trustee under the Indenture shall be deemed incorporated herein by this reference and shall be deemed applicable to all actions taken, suffered or omitted by the Trustee in each of its capacities hereunder, and each agent, custodian and other Person employed to act under this Second Supplemental Indenture.

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IN WITNESS WHEREOF, the parties hereto have caused this Second Supplemental Indenture to be duly executed as of the date first above written.

Attest:

[Signature Page to Hanover—Second Supplemental Indenture]

[Signature Page to Hanover—Second Supplemental Indenture]

EXHIBIT A

THIS NOTE IS A GLOBAL SECURITY WITHIN THE MEANING OF THE INDENTURE HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITARY (AS DEFINED IN THE INDENTURE) OR A NOMINEE THEREOF. THIS GLOBAL SECURITY IS EXCHANGEABLE FOR SECURITIES REGISTERED IN THE NAME OF ANY PERSON OTHER THAN SUCH DEPOSITARY OR ITS NOMINEE ONLY IN LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE AND, UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR SECURITIES IN DEFINITIVE FORM, THIS GLOBAL SECURITY MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE DEPOSITARY TO A NOMINEE OF THE DEPOSITARY, OR BY A NOMINEE OF THE DEPOSITARY TO THE DEPOSITARY OR ANOTHER NOMINEE OF THE DEPOSITARY, OR BY THE DEPOSITARY OR ANY SUCH NOMINEE TO A SUCCESSOR DEPOSITARY OR A NOMINEE OF SUCH SUCCESSOR DEPOSITARY.

UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION (“DTC”), TO THE COMPANY (AS DEFINED BELOW) OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY SECURITY ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR IN SUCH OTHER NAME AS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

THE HANOVER INSURANCE GROUP, INC.

2.500% Note due 2030

The Hanover Insurance Group, Inc., a Delaware corporation (hereinafter called the “Company”, which term includes any successor Person under the Indenture referred to below), for value received, hereby promises to pay to Cede & Co., or registered assigns, the principal sum of Three Hundred Million U.S. Dollars (U.S. $300,000,000) on September 1, 2030 and to pay interest thereon from August 24, 2020 or from the most recent Interest Payment Date to which interest has been paid or duly provided for, semi-annually on March 1 and September 1 in each year (each an “Interest Payment Date”), beginning March 1, 2021 at the rate of 2.500% per annum, until the principal hereof is paid or duly made available for payment. The interest so payable and punctually paid or duly provided for on any Interest Payment Date shall, as provided in such Indenture, be paid to the Person in whose name this Note (or one or more Predecessor Securities) is registered at the close of business on the Regular Record Date for such interest, which shall be the February 15 or August 15 (whether or not a Business Day), as the case may be, next preceding such Interest Payment Date. Any such interest which is payable, but is not punctually paid or duly provided for, on any Interest Payment Date shall forthwith cease to be payable to the Holder hereof on the

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relevant Regular Record Date by virtue of having been such Holder, and may be paid to the Person in whose name this Note (or one or more Predecessor Securities) is registered at the close of business on a Special Record Date for the payment of such Defaulted Interest to be fixed by the Trustee, notice whereof shall be given to Holders of the Notes not less than 10 days prior to such Special Record Date, or may be paid at any time in any other lawful manner not inconsistent with the requirements of any securities exchange on which the Notes may be listed, and upon such notice as may be required by such exchange, all as more fully provided in said Indenture.

Payment of the principal of (and premium, if any) and the interest on this Note shall be made at the designated office of the Trustee (as defined below) at U.S. Bank National Association, One Federal Street, 3^rd Floor, Boston Massachusetts 02110, Attention: Corporate Trust Services, Reference # Hanover 2020 in such currency of the United States of America as at the time of payment is legal tender for payment of public and private debts; provided, however, for so long as the Notes are represented in global form by one or more Global Securities, all payments of principal (and premium, if any) and interest shall be made by wire transfer of immediately available funds to the Depositary or its nominee, as the case may be, as the registered owner of the Global Security representing such Notes. In the event that definitive Notes shall have been issued, all payments of principal (and premium, if any) and interest shall be made at the office of the Paying Agent at One Federal Street, 3rd Floor, Boston, Massachusetts 02110, Attention: Corporate Trust Services, Reference # Hanover 2020; provided, that the Company may at its option pay interest (i) by check to the registered address of each Holder of a definitive Note or (ii) by wire transfer of immediately available funds to the account of any registered Holder thereof, in each of cases (i) and (ii), if such Holder so requests in writing to the Trustee at least 15 days prior to the relevant Interest Payment Date.

This Note is one of the duly authorized series of Securities of the Company, designated as the Company’s “2.500% Notes due 2030”, initially limited to an aggregate principal amount of $300,000,000, all issued or to be issued under and pursuant to an Indenture (the “Base Indenture”), dated as of April 8, 2016, between the Company and U.S. Bank National Association, as Trustee (hereinafter referred to as the “Trustee”), as supplemented by the Second Supplemental Indenture thereto, dated as of August 24, 2020 (the “Second Supplemental Indenture”, and together with the Base Indenture, the “Indenture”). Reference is hereby made to the Indenture for a description of the respective rights, limitation of rights, obligations, duties and immunities thereunder of the Trustee, the Company and the Holders of the Notes.

At any time and from time to time prior to June 1, 2030, the Company may redeem the Notes as a whole or in part, at the Company’s option (an “Optional Redemption”), at a Redemption Price equal to the greater of: (i) 100% of the principal amount of the Notes to be redeemed; and (ii) the sum of the present values of the remaining scheduled payments of principal and interest thereon (exclusive of interest accrued and unpaid to the date of redemption and assuming the notes mature on June 1, 2030) discounted to the Redemption Date on a semiannual basis (assuming a 360-day year consisting of twelve 30-day months) at the Treasury Rate; plus 30 basis points, plus in each case accrued and unpaid interest thereon to, but not including, the date of redemption.

At any time and from time to time on or after June 1, 2030, the Company may redeem the Notes as a whole or in part, at the Company’s option (a “Special Redemption”), at a Redemption Price equal to 100% of the principal amount of the Notes being redeemed, plus in each case accrued and unpaid interest thereon to, but not including, the date of redemption.

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Further installments of interest on the Notes to be redeemed that are due and payable on the Interest Payment Dates falling on or prior to a Redemption Date shall be payable on the Interest Payment Date to the registered Holders as of the close of business on the relevant Regular Record Date.

Notice of any Optional Redemption or Special Redemption will be mailed at least 10 days but not more than 60 days before the Redemption Date to each Holder of Notes to be redeemed; provided, however, that notice of Optional Redemption or Special Redemption may be mailed more than 60 days prior to a Redemption Date if the notice is issued in connection with a defeasance of the Notes or a satisfaction and discharge of Notes.

If less than all of the Notes are to be redeemed, the Notes to be redeemed shall be selected by the Trustee by lot or any other such method as the Trustee deems to be fair and appropriate.

Unless the Company defaults in payment of the Redemption Price, on and after the Redemption Date, interest shall cease to accrue on the Notes or portions thereof called for redemption under an Optional Redemption or Special Redemption.

The Notes are not subject to any sinking fund.

If an Event of Default with respect to the Notes shall occur and be continuing, the principal of the Notes may be declared due and payable in the manner and with the effect provided in the Indenture.

The Indenture permits, with certain exceptions as therein provided, the amendment thereof and the modification of the rights and obligations of the Company and the rights of the Holders of the Securities of each series to be affected under the Indenture at any time by the Company and the Trustee with the consent of the Holders of not less than a majority in aggregate principal amount of the Securities at the time Outstanding of each series affected thereby. The Indenture also contains provisions permitting the Holders of specified percentages in aggregate principal amount of the Securities of any series at the time Outstanding, on behalf of the Holders of all Securities of such series, to waive compliance by the Company with certain provisions of the Indenture and certain past defaults under the Indenture and their consequences. Any such consent or waiver by the Holder of this Note shall be conclusive and binding upon such Holder and upon all future Holders of this Note and of any Note issued upon the registration of transfer hereof or in exchange herefor or in lieu hereof, whether or not notation of such consent or waiver is made upon this Note.

No reference herein to the Indenture and no provision of this Note or of the Indenture shall alter or impair the right of the Holder of this Note, which is absolute and unconditional, to receive payment of the principal of and, subject to certain qualifications in the Indenture, interest on this Note at the times herein and in the Indenture prescribed and to institute suit for the enforcement of any such payment unless the Holder of this Note shall have consented to the impairment of such right.

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As provided in the Indenture and subject to certain limitations set forth therein, the transfer of this Note may be registered in the Security Register, upon surrender of this Note for registration of transfer at the office or agency of the Company in any place where the principal of (and premium, if any) and interest on this Note are payable, duly endorsed by, or accompanied by a written instrument of transfer in form satisfactory to the Company and the Security Registrar duly executed by, the Holder hereof or by his attorney duly authorized in writing, and thereupon one or more new Notes of this series and of any authorized denominations and of a like aggregate principal amount and tenor, shall be issued to the designated transferee or transferees.

The Notes are issuable only in registered form without coupons in denominations of $2,000 and integral multiples of $1,000 in excess thereof. Subject to certain limitations therein set forth in the Indenture and in this Note, the Notes are exchangeable for a like aggregate principal amount of Notes of this series in different authorized denominations, as requested by the Holders surrendering the same.

No service charge shall be made for any such registration of transfer or for exchange of this Note, but the Company or the Trustee may require payment of a sum sufficient to cover any tax or other governmental charge that may be imposed in connection with any registration of transfer or exchange of a Note, other than in certain cases provided in the Indenture.

Prior to due presentment of this Note for registration of transfer, the Company, the Trustee and any agent of the Company or the Trustee may treat the Person in whose name this Note is registered as the owner hereof for all purposes, whether or not this Note be overdue, and neither the Company, the Trustee nor any such agent shall be affected by notice to the contrary.

The Indenture contains provisions whereby (i) the Company may be discharged from its obligations with respect to the Notes (subject to certain exceptions) or (ii) the Company may be released from its obligations under specified covenants and agreements in the Indenture, in each case if the Company irrevocably deposits with the Trustee money or U.S. Government Obligations sufficient to pay and discharge the entire indebtedness on all Notes of this series, and satisfies certain other conditions, all as more fully provided in the Indenture.

This Note shall be governed by and construed in accordance with the laws of the State of New York.

All terms used in this Note which are defined in the Indenture shall have the meanings assigned to them in the Indenture.

Unless the certificate of authentication hereon has been executed by or on behalf of the Trustee under the Indenture by the manual or electronic signature of one of its authorized signatories, this Note shall not be entitled to any benefits under the Indenture or be valid or obligatory for any purpose.

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IN WITNESS WHEREOF, the Company has caused this instrument to be duly executed.

2.500% Note due 2030

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TRUSTEE’S CERTIFICATE OF AUTHENTICATION

This is one of the Securities of the series designated therein referred to in the within-mentioned Indenture.

2.500% Note due 2030

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ABBREVIATIONS

The following abbreviations, when used in the inscription on the face of this instrument, shall be construed as though they were written out in full according to applicable laws or regulations.

[NOTICE: The signature to this assignment must correspond with the name as written upon the face of the within instrument in every particular, without alteration or enlargement or any change whatever.]

2.500% Note due 2030

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