diff --git a/packages/stellar-wallet-snap/CHANGELOG.md b/packages/stellar-wallet-snap/CHANGELOG.md
index 89b43a3c6..3edcd2653 100644
--- a/packages/stellar-wallet-snap/CHANGELOG.md
+++ b/packages/stellar-wallet-snap/CHANGELOG.md
@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- Add `signProofOfOwnership` client request for silent proof-of-ownership signing (SEP-0053) ([#186](https://github.com/MetaMask/internal-snaps/pull/186))
 - Add `TrustlineExceedLimitException` for send simulation when a payment would exceed the destination trustline limit (previously a generic `TransactionValidationException`) ([#185](https://github.com/MetaMask/internal-snaps/pull/185))
 
 ### Changed
diff --git a/packages/stellar-wallet-snap/docs/use-cases/README.md b/packages/stellar-wallet-snap/docs/use-cases/README.md
index ad094cda4..4e553e97a 100644
--- a/packages/stellar-wallet-snap/docs/use-cases/README.md
+++ b/packages/stellar-wallet-snap/docs/use-cases/README.md
@@ -12,6 +12,7 @@ High-level flows for the Stellar Wallet Snap. Each doc focuses on **handlers**,
 | Quote swap / bridge fee             | `computeFee`             | [computeFee.md](./client-request/computeFee.md)                         |
 | Sign & submit swap / bridge         | `signAndSendTransaction` | [signAndSendTransaction.md](./client-request/signAndSendTransaction.md) |
 | Change trustline (opt-in / opt-out) | `changeTrustOpt`         | [changeTrustOpt.md](./client-request/changeTrustOpt.md)                 |
+| Silent proof-of-ownership signing   | `signProofOfOwnership`   | [signProofOfOwnership.md](./client-request/signProofOfOwnership.md)     |
 
 ## Cronjob (`onCronjob`)
 
diff --git a/packages/stellar-wallet-snap/docs/use-cases/client-request/signProofOfOwnership.md b/packages/stellar-wallet-snap/docs/use-cases/client-request/signProofOfOwnership.md
new file mode 100644
index 000000000..38af66d53
--- /dev/null
+++ b/packages/stellar-wallet-snap/docs/use-cases/client-request/signProofOfOwnership.md
@@ -0,0 +1,63 @@
+# Use case: `signProofOfOwnership`
+
+Silently signs a proof-of-ownership message so `@metamask/profile-metrics-controller` can prove the user controls a Stellar address.
+
+|            |                                                                                                                 |
+| ---------- | --------------------------------------------------------------------------------------------------------------- |
+| **Entry**  | `onClientRequest` → `ClientRequestHandler` → `SignProofOfOwnershipHandler`                                      |
+| **Method** | `signProofOfOwnership` (`ClientRequestMethod.SignProofOfOwnership`)                                             |
+| **Source** | [`handlers/clientRequest/signProofOfOwnership.ts`](../../../src/handlers/clientRequest/signProofOfOwnership.ts) |
+
+This is a **silent sign** — there is no confirmation dialog. That is intentional: the MetaMask client needs an ownership proof without interrupting the user. The method is scoped so it cannot be used as a general sign-message bypass:
+
+1. SIP-31 `onClientRequest` is only callable by the MetaMask client.
+2. The plaintext must be `metamask:proof-of-ownership:{nonce}:{address}`, and the embedded address must match the signing account.
+3. Signing uses [SEP-0053](https://github.com/stellar/stellar-protocol/blob/master/ecosystem/sep-0053.md) (`Wallet.signMessage`).
+
+## Request / response (shape)
+
+**Request params**
+
+- `accountId` — keyring account UUID
+- `message` — plaintext `metamask:proof-of-ownership:{nonce}:{address}` (nonce may contain colons; the address is the last `:`-separated field)
+- `nonce`, `address` — coerced from `message` internally (clients do not send these)
+
+**Response**
+
+- `{ signature }` — standard base64 of the 64-byte ed25519 signature (SEP-0053)
+
+## Participants
+
+| Component                     | Path                     | Role in this flow                                    |
+| ----------------------------- | ------------------------ | ---------------------------------------------------- |
+| `ClientRequestHandler`        | `handlers/clientRequest` | Routes `signProofOfOwnership` to the handler         |
+| `SignProofOfOwnershipHandler` | `handlers/clientRequest` | Validates message, resolves wallet, signs            |
+| `AccountResolver`             | `handlers/`              | Loads keyring account + wallet (no on-chain account) |
+| `Wallet`                      | `services/wallet`        | SEP-0053 `signMessage`                               |
+
+## Step-by-step
+
+1. **Route** — `onClientRequest` dispatches to `SignProofOfOwnershipHandler`.
+2. **Validate** — Request must match `SignProofOfOwnershipJsonRpcRequestStruct` (prefix, nonce, Stellar address). `nonce` and `address` are coerced from `message`.
+3. **Resolve** — `BaseClientRequestHandler` loads keyring account and wallet only (`RESOLVE_ACCOUNT_KEYRING_AND_WALLET`). The destination account does not need to be activated on-chain.
+4. **Bind** — The address in the message must equal the signing account address.
+5. **Sign** — `Wallet.signMessage(message)` (SEP-0053, base64).
+
+## Sequence (happy path)
+
+```mermaid
+sequenceDiagram
+  participant Client
+  participant Handler as SignProofOfOwnershipHandler
+  participant Resolver as AccountResolver
+  participant Wallet
+
+  Client->>Handler: signProofOfOwnership { accountId, message }
+  Note over Handler: validate coerces nonce + address from message
+  Handler->>Resolver: resolve keyring account + wallet
+  Resolver-->>Handler: account, wallet
+  Handler->>Handler: message address == account.address
+  Handler->>Wallet: signMessage (SEP-0053, base64)
+  Wallet-->>Handler: signature
+  Handler-->>Client: { signature }
+```
diff --git a/packages/stellar-wallet-snap/snap.manifest.json b/packages/stellar-wallet-snap/snap.manifest.json
index bb45847d4..4ceedbd0a 100644
--- a/packages/stellar-wallet-snap/snap.manifest.json
+++ b/packages/stellar-wallet-snap/snap.manifest.json
@@ -7,7 +7,7 @@
     "url": "https://github.com/MetaMask/internal-snaps.git"
   },
   "source": {
-    "shasum": "SszhtaffKOI/qFUP4XYJU0wGVFGwz/dQAL7pZEONfyI=",
+    "shasum": "I2mbgubtMTDqkgjglt3o7ji1GuNVFYlZ0L0aZNK4Jdw=",
     "location": {
       "npm": {
         "filePath": "dist/bundle.js",
diff --git a/packages/stellar-wallet-snap/src/context.ts b/packages/stellar-wallet-snap/src/context.ts
index 3d13f9d4f..68aa033e5 100644
--- a/packages/stellar-wallet-snap/src/context.ts
+++ b/packages/stellar-wallet-snap/src/context.ts
@@ -15,6 +15,7 @@ import { ConfirmSendHandler } from './handlers/clientRequest/confirmSend';
 import { OnAddressInputHandler } from './handlers/clientRequest/onAddressInput';
 import { OnAmountInputHandler } from './handlers/clientRequest/onAmountInput';
 import { SignAndSendTransactionHandler } from './handlers/clientRequest/signAndSendTransaction';
+import { SignProofOfOwnershipHandler } from './handlers/clientRequest/signProofOfOwnership';
 import type { ICronjobRequestHandler } from './handlers/cronjob/api';
 import { BackgroundEventMethod } from './handlers/cronjob/api';
 import {
@@ -291,6 +292,11 @@ const computeFeeHandler = new ComputeFeeHandler({
   transactionService,
 });
 
+const signProofOfOwnershipHandler = new SignProofOfOwnershipHandler({
+  logger,
+  accountResolver,
+});
+
 const clientRequestMethodHandlers: Record<
   ClientRequestMethod,
   IClientRequestHandler
@@ -301,6 +307,7 @@ const clientRequestMethodHandlers: Record<
   [ClientRequestMethod.ConfirmSend]: confirmSendHandler,
   [ClientRequestMethod.SignAndSendTransaction]: signAndSendTransactionHandler,
   [ClientRequestMethod.ComputeFee]: computeFeeHandler,
+  [ClientRequestMethod.SignProofOfOwnership]: signProofOfOwnershipHandler,
 };
 
 const clientRequestHandler = new ClientRequestHandler({
diff --git a/packages/stellar-wallet-snap/src/handlers/clientRequest/api.test.ts b/packages/stellar-wallet-snap/src/handlers/clientRequest/api.test.ts
index 34fbf1ef9..fbf4e9c04 100644
--- a/packages/stellar-wallet-snap/src/handlers/clientRequest/api.test.ts
+++ b/packages/stellar-wallet-snap/src/handlers/clientRequest/api.test.ts
@@ -21,6 +21,8 @@ import {
   ConfirmSendJsonRpcResponseStruct,
   SignAndSendTransactionJsonRpcRequestStruct,
   SignAndSendTransactionJsonRpcResponseStruct,
+  SignProofOfOwnershipJsonRpcRequestStruct,
+  SignProofOfOwnershipJsonRpcResponseStruct,
 } from './api';
 
 const accountId = '11111111-1111-4111-8111-111111111111';
@@ -918,3 +920,147 @@ describe('ConfirmSendJsonRpcResponseStruct', () => {
     );
   });
 });
+
+describe('SignProofOfOwnershipJsonRpcRequestStruct', () => {
+  const nonce = 'a1b2c3d4e5f6789012345678';
+
+  it.each([
+    {
+      message: `metamask:proof-of-ownership:${nonce}:${stellarAddress}`,
+      nonce,
+      address: stellarAddress,
+    },
+    {
+      message: `metamask:proof-of-ownership:abc-DEF_123:${stellarAddress}`,
+      nonce: 'abc-DEF_123',
+      address: stellarAddress,
+    },
+    {
+      message: `metamask:proof-of-ownership:ns:abc:123:${stellarAddress}`,
+      nonce: 'ns:abc:123',
+      address: stellarAddress,
+    },
+  ])(
+    'accepts a valid signProofOfOwnership request: "$message"',
+    ({ message, nonce: expectedNonce, address }) => {
+      const result = create(
+        {
+          jsonrpc: '2.0',
+          id: 1,
+          method: ClientRequestMethod.SignProofOfOwnership,
+          params: { accountId, message },
+        },
+        SignProofOfOwnershipJsonRpcRequestStruct,
+      );
+
+      expect(result.params).toStrictEqual({
+        accountId,
+        message,
+        nonce: expectedNonce,
+        address,
+      });
+    },
+  );
+
+  it.each([
+    {
+      method: ClientRequestMethod.ConfirmSend,
+      params: {
+        accountId,
+        message: `metamask:proof-of-ownership:${nonce}:${stellarAddress}`,
+      },
+    },
+    {
+      method: ClientRequestMethod.SignProofOfOwnership,
+      params: { accountId },
+    },
+    {
+      method: ClientRequestMethod.SignProofOfOwnership,
+      params: { accountId, message: `rewards,${stellarAddress},123` },
+    },
+    {
+      method: ClientRequestMethod.SignProofOfOwnership,
+      params: {
+        accountId,
+        message: `metamask:proof:${nonce}:${stellarAddress}`,
+      },
+    },
+    {
+      method: ClientRequestMethod.SignProofOfOwnership,
+      params: {
+        accountId,
+        message: `Metamask:proof-of-ownership:${nonce}:${stellarAddress}`,
+      },
+    },
+    {
+      method: ClientRequestMethod.SignProofOfOwnership,
+      params: { accountId, message: `${nonce}:${stellarAddress}` },
+    },
+    {
+      method: ClientRequestMethod.SignProofOfOwnership,
+      params: { accountId, message: '' },
+    },
+    {
+      method: ClientRequestMethod.SignProofOfOwnership,
+      params: { accountId, message: `metamask:proof-of-ownership:${nonce}` },
+    },
+    {
+      method: ClientRequestMethod.SignProofOfOwnership,
+      params: {
+        accountId,
+        message: `metamask:proof-of-ownership::${stellarAddress}`,
+      },
+    },
+    {
+      method: ClientRequestMethod.SignProofOfOwnership,
+      params: { accountId, message: `metamask:proof-of-ownership:${nonce}:` },
+    },
+    {
+      method: ClientRequestMethod.SignProofOfOwnership,
+      params: {
+        accountId,
+        message: `metamask:proof-of-ownership:${nonce}:not-a-stellar-address`,
+      },
+    },
+    {
+      method: ClientRequestMethod.SignProofOfOwnership,
+      params: {
+        accountId,
+        message: `metamask:proof-of-ownership:${nonce}:0x1234567890abcdef1234567890abcdef12345678`,
+      },
+    },
+  ])(
+    'rejects an invalid signProofOfOwnership request',
+    ({ method, params }) => {
+      expect(() =>
+        assert(
+          { jsonrpc: '2.0', id: 1, method, params },
+          SignProofOfOwnershipJsonRpcRequestStruct,
+        ),
+      ).toThrow(StructError);
+    },
+  );
+});
+
+describe('SignProofOfOwnershipJsonRpcResponseStruct', () => {
+  it('accepts a standard base64 signature', () => {
+    expect(() =>
+      assert(
+        {
+          signature:
+            'fO5dbYhXUhBMhe6kId/cuVq/AfEnHRHEvsP8vXh03M1uLpi5e46yO2Q8rEBzu3feXQewcQE5GArp88u6ePK6BA==',
+        },
+        SignProofOfOwnershipJsonRpcResponseStruct,
+      ),
+    ).not.toThrow();
+  });
+
+  it.each([{ signature: 'not!!!valid-base64' }, { signature: '' }, {}])(
+    'rejects an invalid signProofOfOwnership response',
+    (response) => {
+      expect(() =>
+        assert(response, SignProofOfOwnershipJsonRpcResponseStruct),
+      ).toThrow(StructError);
+    },
+  );
+});
diff --git a/packages/stellar-wallet-snap/src/handlers/clientRequest/api.ts b/packages/stellar-wallet-snap/src/handlers/clientRequest/api.ts
index fd1bec48a..1907f9e46 100644
--- a/packages/stellar-wallet-snap/src/handlers/clientRequest/api.ts
+++ b/packages/stellar-wallet-snap/src/handlers/clientRequest/api.ts
@@ -18,7 +18,11 @@ import {
   coerce,
 } from '@metamask/superstruct';
 import type { JsonRpcRequest } from '@metamask/utils';
-import { CaipAssetTypeStruct, parseCaipAssetType } from '@metamask/utils';
+import {
+  base64,
+  CaipAssetTypeStruct,
+  parseCaipAssetType,
+} from '@metamask/utils';
 
 import {
   JsonRpcRequestStruct,
@@ -36,6 +40,7 @@ import {
   SwapTransactionXdrStruct,
 } from '../../api';
 import { isSep41Id } from '../../utils';
+import { parseProofOfOwnershipMessage } from './utils';
 
 /**
  * Enum for the client request method.
@@ -48,6 +53,11 @@ export enum ClientRequestMethod {
   // Standard multichain workflow for bridge
   SignAndSendTransaction = 'signAndSendTransaction',
   ComputeFee = 'computeFee',
+  /**
+   * Silent proof-of-ownership signing for `@metamask/profile-metrics-controller`.
+   * SIP-31 client-only.
+   */
+  SignProofOfOwnership = 'signProofOfOwnership',
   /** -------------------------------- Stellar Specific -------------------------------- */
   ChangeTrustOpt = 'changeTrustOpt',
 }
@@ -375,6 +385,69 @@ export const ComputeFeeJsonRpcResponseStruct = array(
   }),
 );
 
+/**
+ * Validates that a plaintext message follows the proof-of-ownership format:
+ * `'metamask:proof-of-ownership:{nonce}:{address}'`.
+ */
+export const ProofOfOwnershipMessageStruct = refine(
+  string(),
+  'ProofOfOwnershipMessage',
+  (value: string) => {
+    try {
+      parseProofOfOwnershipMessage(value);
+      return true;
+    } catch (error) {
+      return error instanceof Error
+        ? error.message
+        : 'Invalid proof-of-ownership message';
+    }
+  },
+);
+
+/**
+ * Validation struct for the signProofOfOwnership JSON-RPC request.
+ * Coerces `nonce` and `address` from `message` (clients send only accountId + message).
+ */
+export const SignProofOfOwnershipJsonRpcRequestStruct = coerce(
+  assign(
+    JsonRpcRequestStruct,
+    object({
+      method: literal(ClientRequestMethod.SignProofOfOwnership),
+      params: object({
+        accountId: UuidStruct,
+        message: ProofOfOwnershipMessageStruct,
+        nonce: nonempty(string()),
+        address: StellarAddressStruct,
+      }),
+    }),
+  ),
+  assign(
+    JsonRpcRequestStruct,
+    object({
+      method: literal(ClientRequestMethod.SignProofOfOwnership),
+      params: object({
+        accountId: UuidStruct,
+        message: ProofOfOwnershipMessageStruct,
+      }),
+    }),
+  ),
+  (request) => ({
+    ...request,
+    params: {
+      ...request.params,
+      ...parseProofOfOwnershipMessage(request.params.message),
+    },
+  }),
+);
+
+/**
+ * Validation struct for the signProofOfOwnership JSON-RPC response.
+ * Standard base64 of the 64-byte ed25519 signature (SEP-0053).
+ */
+export const SignProofOfOwnershipJsonRpcResponseStruct = object({
+  signature: nonempty(base64(string())),
+});
+
 /**
  * A JSON-RPC request with an account resolve parameter.
  */
@@ -466,3 +539,17 @@ export type ComputeFeeJsonRpcRequest = Infer<
 export type ComputeFeeJsonRpcResponse = Infer<
   typeof ComputeFeeJsonRpcResponseStruct
 >;
+
+/**
+ * Type for the signProofOfOwnership JSON-RPC request.
+ */
+export type SignProofOfOwnershipJsonRpcRequest = Infer<
+  typeof SignProofOfOwnershipJsonRpcRequestStruct
+>;
+
+/**
+ * Type for the signProofOfOwnership JSON-RPC response.
+ */
+export type SignProofOfOwnershipJsonRpcResponse = Infer<
+  typeof SignProofOfOwnershipJsonRpcResponseStruct
+>;
diff --git a/packages/stellar-wallet-snap/src/handlers/clientRequest/signProofOfOwnership.test.ts b/packages/stellar-wallet-snap/src/handlers/clientRequest/signProofOfOwnership.test.ts
new file mode 100644
index 000000000..82eae88ad
--- /dev/null
+++ b/packages/stellar-wallet-snap/src/handlers/clientRequest/signProofOfOwnership.test.ts
@@ -0,0 +1,121 @@
+import type { JsonRpcRequest } from '@metamask/utils';
+
+import { AccountService, StellarKeyringAccount } from '../../services/account';
+import { generateStellarKeyringAccount } from '../../services/account/__mocks__/account.fixtures';
+import { mockOnChainAccountService } from '../../services/on-chain-account/__mocks__/onChainAccount.fixtures';
+import { Wallet, WalletService } from '../../services/wallet';
+import { getTestWallet } from '../../services/wallet/__mocks__/wallet.fixtures';
+import { logger } from '../../utils/logger';
+import { AccountResolver } from '../accountResolver';
+import { ClientRequestMethod } from './api';
+import { SignProofOfOwnershipHandler } from './signProofOfOwnership';
+
+jest.mock('../../utils/logger');
+
+describe('SignProofOfOwnershipHandler', () => {
+  const accountId = '11111111-1111-4111-8111-111111111111';
+  const nonce = 'a1b2c3d4e5f6789012345678';
+
+  type SetupResult = {
+    handler: SignProofOfOwnershipHandler;
+    account: StellarKeyringAccount;
+    wallet: Wallet;
+    resolveAccountSpy: jest.SpyInstance;
+    resolveWalletSpy: jest.SpyInstance;
+    buildProofMessage: (proofNonce?: string, proofAddress?: string) => string;
+    createRequest: (message?: string) => JsonRpcRequest;
+  };
+
+  afterEach(() => {
+    jest.restoreAllMocks();
+  });
+
+  function setup(): SetupResult {
+    const wallet = getTestWallet();
+    const account = generateStellarKeyringAccount(
+      accountId,
+      wallet.address,
+      'entropy-source-1',
+      0,
+    );
+
+    const { accountService, onChainAccountService, walletService } =
+      mockOnChainAccountService();
+    const accountResolver = new AccountResolver({
+      accountService,
+      onChainAccountService,
+      walletService,
+    });
+
+    const resolveAccountSpy = jest
+      .spyOn(AccountService.prototype, 'resolveAccount')
+      .mockResolvedValue({ account });
+
+    const resolveWalletSpy = jest
+      .spyOn(WalletService.prototype, 'resolveWallet')
+      .mockResolvedValue(wallet);
+
+    const handler = new SignProofOfOwnershipHandler({
+      logger,
+      accountResolver,
+    });
+
+    const buildProofMessage = (
+      proofNonce: string = nonce,
+      proofAddress: string = wallet.address,
+    ): string => `metamask:proof-of-ownership:${proofNonce}:${proofAddress}`;
+
+    const createRequest = (message?: string): JsonRpcRequest => ({
+      jsonrpc: '2.0',
+      id: 1,
+      method: ClientRequestMethod.SignProofOfOwnership,
+      params: {
+        accountId,
+        message: message ?? buildProofMessage(),
+      },
+    });
+
+    return {
+      handler,
+      account,
+      wallet,
+      resolveAccountSpy,
+      resolveWalletSpy,
+      buildProofMessage,
+      createRequest,
+    };
+  }
+
+  it('signs the proof message and returns the SEP-0053 base64 signature', async () => {
+    const {
+      handler,
+      wallet,
+      resolveAccountSpy,
+      resolveWalletSpy,
+      buildProofMessage,
+      createRequest,
+    } = setup();
+    const message = buildProofMessage();
+
+    const result = await handler.handle(createRequest());
+
+    expect(resolveAccountSpy).toHaveBeenCalledWith({ accountId });
+    expect(resolveWalletSpy).toHaveBeenCalled();
+    expect(result).toStrictEqual({
+      signature: wallet.signMessage(message),
+    });
+    expect(wallet.verifyMessage(message, result.signature)).toBe(true);
+  });
+
+  it('throws if the address in the message does not match the signing account', async () => {
+    const { handler, wallet, createRequest, buildProofMessage } = setup();
+    const otherWallet = getTestWallet();
+    const otherAddress = otherWallet.address;
+
+    await expect(
+      handler.handle(createRequest(buildProofMessage(nonce, otherAddress))),
+    ).rejects.toThrow(
+      `Address in proof-of-ownership message (${otherAddress}) does not match signing account address (${wallet.address})`,
+    );
+  });
+});
diff --git a/packages/stellar-wallet-snap/src/handlers/clientRequest/signProofOfOwnership.ts b/packages/stellar-wallet-snap/src/handlers/clientRequest/signProofOfOwnership.ts
new file mode 100644
index 000000000..14b6c4bd6
--- /dev/null
+++ b/packages/stellar-wallet-snap/src/handlers/clientRequest/signProofOfOwnership.ts
@@ -0,0 +1,85 @@
+import { InvalidParamsError } from '@metamask/snaps-sdk';
+
+import { createPrefixedLogger } from '../../utils/logger';
+import type { ILogger } from '../../utils/logger';
+import type { AccountResolver } from '../accountResolver';
+import { RESOLVE_ACCOUNT_KEYRING_AND_WALLET } from '../accountResolver';
+import { BaseHandler } from '../base';
+import type {
+  SignProofOfOwnershipJsonRpcRequest,
+  SignProofOfOwnershipJsonRpcResponse,
+} from './api';
+import {
+  SignProofOfOwnershipJsonRpcRequestStruct,
+  SignProofOfOwnershipJsonRpcResponseStruct,
+} from './api';
+import type { IClientRequestHandler } from './base';
+
+/**
+ * Handles the silent signing of a proof-of-ownership message, of format
+ * `'metamask:proof-of-ownership:{nonce}:{address}'`.
+ *
+ * Used by `@metamask/profile-metrics-controller` to prove wallet control of an
+ * address. This is a **silent sign** (no user confirmation dialog): it skips
+ * the usual sign-message security prompt on purpose so the client can collect
+ * profile-metrics ownership proofs without interrupting the user.
+ *
+ */
+export class SignProofOfOwnershipHandler
+  // We don't need to resolve an on-chain account for this handler,
+  // so we can use the base handler without any additional options.
+  extends BaseHandler<
+    SignProofOfOwnershipJsonRpcRequest,
+    SignProofOfOwnershipJsonRpcResponse
+  >
+  implements IClientRequestHandler
+{
+  readonly #accountResolver: AccountResolver;
+
+  constructor({
+    logger,
+    accountResolver,
+  }: {
+    logger: ILogger;
+    accountResolver: AccountResolver;
+  }) {
+    super({
+      logger: createPrefixedLogger(logger, '[🔏 SignProofOfOwnershipHandler]'),
+      requestStruct: SignProofOfOwnershipJsonRpcRequestStruct,
+      responseStruct: SignProofOfOwnershipJsonRpcResponseStruct,
+    });
+    this.#accountResolver = accountResolver;
+  }
+
+  /**
+   * Resolves the keyring account + wallet (no on-chain activation required)
+   * and signs the validated proof message.
+   *
+   * @param request - The JSON-RPC request containing `accountId`, `message`,
+   * and coerced `address`.
+   * @returns `{ signature }` as standard base64 of the SEP-0053 ed25519 signature.
+   * @throws {InvalidParamsError} If the address in the message does not match
+   * the signing account.
+   */
+  protected async handleRequest(
+    request: SignProofOfOwnershipJsonRpcRequest,
+  ): Promise<SignProofOfOwnershipJsonRpcResponse> {
+    const { accountId, message, address: messageAddress } = request.params;
+
+    const { account, wallet } = await this.#accountResolver.resolveAccount({
+      accountId,
+      options: RESOLVE_ACCOUNT_KEYRING_AND_WALLET,
+    });
+
+    if (messageAddress !== account.address) {
+      // eslint-disable-next-line @typescript-eslint/only-throw-error -- InvalidParamsError is the JSON-RPC snap error surface
+      throw new InvalidParamsError(
+        `Address in proof-of-ownership message (${messageAddress}) does not match signing account address (${account.address})`,
+      );
+    }
+
+    return {
+      signature: wallet.signMessage(message),
+    };
+  }
+}
diff --git a/packages/stellar-wallet-snap/src/handlers/clientRequest/utils.ts b/packages/stellar-wallet-snap/src/handlers/clientRequest/utils.ts
index b4dec26c8..4b4390e5f 100644
--- a/packages/stellar-wallet-snap/src/handlers/clientRequest/utils.ts
+++ b/packages/stellar-wallet-snap/src/handlers/clientRequest/utils.ts
@@ -1,3 +1,4 @@
+import { StellarAddressStruct } from '../../api/address';
 import { TransactionValidationException } from '../../services/transaction';
 import type { Transaction } from '../../services/transaction';
 
@@ -27,3 +28,46 @@ export function assertRefreshedTransactionFeeNotHigher(params: {
     );
   }
 }
+
+/**
+ * Parses a proof-of-ownership message of format
+ * `'metamask:proof-of-ownership:{nonce}:{address}'`.
+ * Splits on the last `:` so opaque nonces may contain colons.
+ *
+ * @param message - The plaintext proof-of-ownership message.
+ * @returns The parsed nonce and Stellar address.
+ * @throws Error if the message format is invalid.
+ */
+export function parseProofOfOwnershipMessage(message: string): {
+  nonce: string;
+  address: string;
+} {
+  const messagePrefix = 'metamask:proof-of-ownership:';
+
+  if (!message.startsWith(messagePrefix)) {
+    throw new Error(`Message must start with "${messagePrefix}"`);
+  }
+
+  const remainder = message.slice(messagePrefix.length);
+  const separatorIdx = remainder.lastIndexOf(':');
+  if (separatorIdx === -1) {
+    throw new Error(
+      'Message must follow the format "metamask:proof-of-ownership:{nonce}:{address}"',
+    );
+  }
+
+  const nonce = remainder.slice(0, separatorIdx);
+  const address = remainder.slice(separatorIdx + 1);
+
+  if (nonce === '') {
+    throw new Error(
+      'Proof-of-ownership message must contain a non-empty nonce',
+    );
+  }
+
+  if (!StellarAddressStruct.is(address)) {
+    throw new Error('Invalid Stellar address in proof-of-ownership message');
+  }
+
+  return { nonce, address };
+}