diff --git a/docs/github-releases.md b/docs/github-releases.md
index d409274a..fe8dde71 100644
--- a/docs/github-releases.md
+++ b/docs/github-releases.md
@@ -64,7 +64,12 @@ command-line directly: `--github.releaseName="Arcade Silver"`.
 
 By default, the output of `git.changelog` is used for the GitHub release notes. This is the printed `Changelog: ...`
 when release-it boots. This can be overridden with the `github.releaseNotes` option to customize the release notes for
-the GitHub release. This script will run just before the actual GitHub release itself. Make sure it outputs to `stdout`.
+the GitHub release. This will be invoked just before the actual GitHub release itself.
+
+The value can either be a string or a function but a function is only supported when configuring release-it using
+`.release-it.js` or `.release-it.cjs` file.
+
+When the value is a string, it's executed as a shell script. Make sure it outputs to `stdout`.
 An example:
 
 ```json
@@ -76,6 +81,22 @@ An example:
 }
 ```
 
+When the value is a function, it's executed with a single `context` parameter that contains the plugin context.
+The function can also be `async`. Make sure that it returns a string value.
+An example:
+
+```js
+{
+  github: {
+    release: true,
+    releaseNotes(context) {
+      // Remove the first, redundant line with version and date.
+      return context.changelog.split('\n').slice(1).join('\n');
+    }
+  }
+}
+```
+
 Use `--github.autoGenerate` to have GitHub auto-generate the release notes.
 
 See [Changelog](./changelog.md) for more information about generating changelogs/release notes.
diff --git a/docs/gitlab-releases.md b/docs/gitlab-releases.md
index 9f5ce3e0..8c57ef01 100644
--- a/docs/gitlab-releases.md
+++ b/docs/gitlab-releases.md
@@ -26,7 +26,12 @@ To skip these checks, use `gitlab.skipChecks`.
 
 By default, the output of `git.changelog` is used for the GitLab release notes. This is the printed `Changelog: ...`
 when release-it boots. This can be overridden with the `gitlab.releaseNotes` option to customize the release notes for
-the GitLab release. This script will run just before the actual GitLab release itself. Make sure it outputs to `stdout`.
+the GitLab release.  This will be invoked just before the actual GitLab release itself.
+
+The value can either be a string or a function but a function is only supported when configuring release-it using
+`.release-it.js` or `.release-it.cjs` file.
+
+When the value is a string, it's executed as a shell script. Make sure it outputs to `stdout`.
 An example:
 
 ```json
@@ -38,6 +43,22 @@ An example:
 }
 ```
 
+When the value is a function, it's executed with a single `context` parameter that contains the plugin context.
+The function can also be `async`. Make sure that it returns a string value.
+An example:
+
+```js
+{
+  gitlab: {
+    release: true,
+    releaseNotes(context) {
+      // Remove the first, redundant line with version and date.
+      return context.changelog.split('\n').slice(1).join('\n');
+    }
+  }
+}
+```
+
 See [Changelog](./changelog.md) for more information about generating changelogs/release notes.
 
 ## Milestones
diff --git a/lib/plugin/GitRelease.js b/lib/plugin/GitRelease.js
index 205a6ffa..27e94c43 100644
--- a/lib/plugin/GitRelease.js
+++ b/lib/plugin/GitRelease.js
@@ -24,13 +24,22 @@ class GitRelease extends GitBase {
   async beforeRelease() {
     const { releaseNotes: script } = this.options;
     const { changelog } = this.config.getContext();
-    const releaseNotes = script ? await this.exec(script) : changelog;
+    const releaseNotes = script ? await this.processReleaseNotes(script) : changelog;
     this.setContext({ releaseNotes });
     if (releaseNotes !== changelog) {
       this.log.preview({ title: 'release notes', text: releaseNotes });
     }
   }
 
+  async processReleaseNotes(script) {
+    if (typeof script === 'function') {
+      const ctx = Object.assign({}, this.config.getContext(), { [this.namespace]: this.getContext() });
+      return await script(ctx);
+    } else {
+      return await this.exec(script);
+    }
+  }
+
   afterRelease() {
     const { isReleased, releaseUrl } = this.getContext();
     if (isReleased) {
diff --git a/test/github.js b/test/github.js
index 124b9bcb..9f7c5f1a 100644
--- a/test/github.js
+++ b/test/github.js
@@ -164,6 +164,35 @@ test('should update release and upload assets', async t => {
   exec.restore();
 });
 
+test('should create custom release notes using releaseNotes function', async t => {
+  const options = {
+    git,
+    github: {
+      pushRepo,
+      tokenRef,
+      release: true,
+      releaseName: 'Release ${tagName}',
+      releaseNotes(context) {
+        return `Custom notes for tag ${context.tagName}`;
+      }
+    }
+  };
+  const github = factory(GitHub, { options });
+  const exec = sinon.stub(github.shell, 'exec').callThrough();
+  exec.withArgs('git describe --tags --match=* --abbrev=0').resolves('2.0.1');
+
+  interceptAuthentication();
+  interceptCollaborator();
+  interceptCreate({ body: { tag_name: '2.0.2', name: 'Release 2.0.2', body: 'Custom notes for tag 2.0.2' } });
+
+  await runTasks(github);
+
+  const { isReleased, releaseUrl } = github.getContext();
+  t.true(isReleased);
+  t.is(releaseUrl, 'https://github.com/user/repo/releases/tag/2.0.2');
+  exec.restore();
+});
+
 test('should create new release for unreleased tag', async t => {
   const options = {
     increment: false,