diff --git a/README.md b/README.md
index c3f17b7fd6..41e5c97234 100644
--- a/README.md
+++ b/README.md
@@ -55,7 +55,7 @@ All inputs are **optional**. If not set, sensible defaults will be used.
 | `path` | Relative path under `GITHUB_WORKSPACE` to the repository. | `GITHUB_WORKSPACE` |
 | `add-paths` | A comma or newline-separated list of file paths to commit. Paths should follow git's [pathspec](https://git-scm.com/docs/gitglossary#Documentation/gitglossary.txt-aiddefpathspecapathspec) syntax. See [Add specific paths](#add-specific-paths). | If no paths are specified, all new and modified files are added. |
 | `commit-message` | The message to use when committing changes. See [commit-message](#commit-message). | `[create-pull-request] automated change` |
-| `committer` | The committer name and email address in the format `Display Name <email@address.com>`. Defaults to the GitHub Actions bot user on github.com. | `github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>` |
+| `committer` | The committer name and email address in the format `Display Name <email@address.com>`. Defaults to the identity of the `token` | `github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>` for the GitHub Actions bot user on github.com |
 | `author` | The author name and email address in the format `Display Name <email@address.com>`. Defaults to the user who triggered the workflow run. | `${{ github.actor }} <${{ github.actor_id }}+${{ github.actor }}@users.noreply.github.com>` |
 | `signoff` | Add [`Signed-off-by`](https://git-scm.com/docs/git-commit#Documentation/git-commit.txt---signoff) line by the committer at the end of the commit log message. | `false` |
 | `branch` | The pull request branch name. | `create-pull-request/patch` |
diff --git a/__test__/utils.unit.test.ts b/__test__/utils.unit.test.ts
index 2381b98e30..4f44d5ccb4 100644
--- a/__test__/utils.unit.test.ts
+++ b/__test__/utils.unit.test.ts
@@ -117,6 +117,38 @@ describe('utils tests', () => {
       )
     }
   })
+
+  test('composeNoReplyIdentity produces the unchanged github.com identity', async () => {
+    const identity = utils.composeNoReplyIdentity(
+      'github-actions[bot]',
+      41898282,
+      'github.com'
+    )
+    expect(identity).toEqual(
+      'github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>'
+    )
+    const parsed = utils.parseDisplayNameEmail(identity)
+    expect(parsed.name).toEqual('github-actions[bot]')
+    expect(parsed.email).toEqual(
+      '41898282+github-actions[bot]@users.noreply.github.com'
+    )
+  })
+
+  test('composeNoReplyIdentity derives a server-aware identity on GHES', async () => {
+    const identity = utils.composeNoReplyIdentity(
+      'github-actions[bot]',
+      5,
+      'ghe.example.com'
+    )
+    expect(identity).toEqual(
+      'github-actions[bot] <5+github-actions[bot]@users.noreply.ghe.example.com>'
+    )
+    const parsed = utils.parseDisplayNameEmail(identity)
+    expect(parsed.name).toEqual('github-actions[bot]')
+    expect(parsed.email).toEqual(
+      '5+github-actions[bot]@users.noreply.ghe.example.com'
+    )
+  })
 })
 
 describe('retryWithBackoff', () => {
diff --git a/action.yml b/action.yml
index e09c1f3ba9..fecbacdd5b 100644
--- a/action.yml
+++ b/action.yml
@@ -23,13 +23,12 @@ inputs:
   committer:
     description: >
       The committer name and email address in the format `Display Name <email@address.com>`.
-      Defaults to the GitHub Actions bot user.
-    default: 'github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>'
+      Defaults to the identity of the `token` (e.g. `github-actions[bot]` for `GITHUB_TOKEN`,
+      your app's bot for a GitHub App token, or the user for a PAT).
   author:
     description: >
       The author name and email address in the format `Display Name <email@address.com>`.
-      Defaults to the user who triggered the workflow run.
-    default: '${{ github.actor }} <${{ github.actor_id }}+${{ github.actor }}@users.noreply.github.com>'
+      Defaults to the user who triggered the workflow run, with a server-aware no-reply email.
   signoff:
     description: 'Add `Signed-off-by` line by the committer at the end of the commit log message.'
     default: false
diff --git a/dist/index.js b/dist/index.js
index c06637d71d..00f9e29cda 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -491,6 +491,31 @@ function createPullRequest(inputs) {
             core.info(`Pull request branch to create or update set to '${inputs.branch}'`);
             // Configure the committer and author
             core.startGroup('Configuring the committer and author');
+            // Resolve the default committer from the token identity
+            if (!inputs.committer) {
+                try {
+                    const user = yield ghBranch.getServerUser();
+                    inputs.committer = utils.composeNoReplyIdentity(user.login, user.id, baseRemote.hostname);
+                    core.info(`Committer not supplied; derived from token as '${inputs.committer}'`);
+                }
+                catch (e) {
+                    core.warning(`Failed to derive committer from token: ${utils.getErrorMessage(e)}`);
+                    inputs.committer =
+                        'github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>';
+                }
+            }
+            // Resolve the author default from the triggering actor, with a server-aware
+            // no-reply email domain.
+            if (!inputs.author) {
+                const actor = process.env['GITHUB_ACTOR'];
+                const actorId = process.env['GITHUB_ACTOR_ID'];
+                if (actor && actorId) {
+                    inputs.author = utils.composeNoReplyIdentity(actor, actorId, baseRemote.hostname);
+                }
+                else {
+                    inputs.author = inputs.committer;
+                }
+            }
             const parsedAuthor = utils.parseDisplayNameEmail(inputs.author);
             const parsedCommitter = utils.parseDisplayNameEmail(inputs.committer);
             git.setIdentityGitOptions([
@@ -1406,6 +1431,21 @@ class GitHubHelper {
             repo: repo
         };
     }
+    getServerUser() {
+        return __awaiter(this, void 0, void 0, function* () {
+            var _a, _b;
+            // Resolve the identity behind the authenticated token.
+            // The GraphQL `viewer` resolves installation tokens (the default
+            // `GITHUB_TOKEN` and GitHub App tokens) as well as PAT tokens.
+            // REST `users.getAuthenticated()` is NOT used since it does not work for
+            // installation tokens.
+            const resp = yield this.octokit.graphql(`query { viewer { login databaseId } }`);
+            if (!((_a = resp === null || resp === void 0 ? void 0 : resp.viewer) === null || _a === void 0 ? void 0 : _a.login) || !((_b = resp === null || resp === void 0 ? void 0 : resp.viewer) === null || _b === void 0 ? void 0 : _b.databaseId)) {
+                throw new Error('GraphQL viewer did not return login and databaseId');
+            }
+            return { login: resp.viewer.login, id: resp.viewer.databaseId };
+        });
+    }
     getPullNumber(baseRepository, headBranch, baseBranch) {
         return __awaiter(this, void 0, void 0, function* () {
             var _a, e_1, _b, _c;
@@ -1929,6 +1969,7 @@ exports.getRepoPath = getRepoPath;
 exports.getRemoteUrl = getRemoteUrl;
 exports.secondsSinceEpoch = secondsSinceEpoch;
 exports.randomString = randomString;
+exports.composeNoReplyIdentity = composeNoReplyIdentity;
 exports.parseDisplayNameEmail = parseDisplayNameEmail;
 exports.fileExistsSync = fileExistsSync;
 exports.readFile = readFile;
@@ -1980,6 +2021,11 @@ function secondsSinceEpoch() {
 function randomString() {
     return Math.random().toString(36).substr(2, 7);
 }
+function composeNoReplyIdentity(login, id, hostname) {
+    // The GitHub no-reply commit identity, e.g.
+    // `github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>`.
+    return `${login} <${id}+${login}@users.noreply.${hostname}>`;
+}
 function parseDisplayNameEmail(displayNameEmail) {
     // Parse the name and email address from a string in the following format
     // Display Name <email@address.com>
diff --git a/src/create-pull-request.ts b/src/create-pull-request.ts
index 2e3f0e0a29..9c814bd160 100644
--- a/src/create-pull-request.ts
+++ b/src/create-pull-request.ts
@@ -168,6 +168,41 @@ export async function createPullRequest(inputs: Inputs): Promise<void> {
 
     // Configure the committer and author
     core.startGroup('Configuring the committer and author')
+    // Resolve the default committer from the token identity
+    if (!inputs.committer) {
+      try {
+        const user = await ghBranch.getServerUser()
+        inputs.committer = utils.composeNoReplyIdentity(
+          user.login,
+          user.id,
+          baseRemote.hostname
+        )
+        core.info(
+          `Committer not supplied; derived from token as '${inputs.committer}'`
+        )
+      } catch (e) {
+        core.warning(
+          `Failed to derive committer from token: ${utils.getErrorMessage(e)}`
+        )
+        inputs.committer =
+          'github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>'
+      }
+    }
+    // Resolve the author default from the triggering actor, with a server-aware
+    // no-reply email domain.
+    if (!inputs.author) {
+      const actor = process.env['GITHUB_ACTOR']
+      const actorId = process.env['GITHUB_ACTOR_ID']
+      if (actor && actorId) {
+        inputs.author = utils.composeNoReplyIdentity(
+          actor,
+          actorId,
+          baseRemote.hostname
+        )
+      } else {
+        inputs.author = inputs.committer
+      }
+    }
     const parsedAuthor = utils.parseDisplayNameEmail(inputs.author)
     const parsedCommitter = utils.parseDisplayNameEmail(inputs.committer)
     git.setIdentityGitOptions([
diff --git a/src/github-helper.ts b/src/github-helper.ts
index 26ef65cb87..1469fbfc87 100644
--- a/src/github-helper.ts
+++ b/src/github-helper.ts
@@ -37,6 +37,11 @@ interface CommitResponse {
   verified: boolean
 }
 
+interface TokenIdentity {
+  login: string
+  id: number
+}
+
 type TreeObject = {
   path: string
   mode: '100644' | '100755' | '040000' | '160000' | '120000'
@@ -70,6 +75,21 @@ export class GitHubHelper {
     }
   }
 
+  async getServerUser(): Promise<TokenIdentity> {
+    // Resolve the identity behind the authenticated token.
+    // The GraphQL `viewer` resolves installation tokens (the default
+    // `GITHUB_TOKEN` and GitHub App tokens) as well as PAT tokens.
+    // REST `users.getAuthenticated()` is NOT used since it does not work for
+    // installation tokens.
+    const resp = await this.octokit.graphql<{
+      viewer: {login: string; databaseId: number}
+    }>(`query { viewer { login databaseId } }`)
+    if (!resp?.viewer?.login || !resp?.viewer?.databaseId) {
+      throw new Error('GraphQL viewer did not return login and databaseId')
+    }
+    return {login: resp.viewer.login, id: resp.viewer.databaseId}
+  }
+
   private async getPullNumber(
     baseRepository: string,
     headBranch: string,
diff --git a/src/utils.ts b/src/utils.ts
index a7f825d8b3..84c89efb69 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -65,6 +65,16 @@ interface DisplayNameEmail {
   email: string
 }
 
+export function composeNoReplyIdentity(
+  login: string,
+  id: number | string,
+  hostname: string
+): string {
+  // The GitHub no-reply commit identity, e.g.
+  // `github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>`.
+  return `${login} <${id}+${login}@users.noreply.${hostname}>`
+}
+
 export function parseDisplayNameEmail(
   displayNameEmail: string
 ): DisplayNameEmail {