diff --git a/HISTORY.md b/HISTORY.md
index 1748679..b7271e4 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -1,3 +1,8 @@
+unreleased
+==========
+
+  * Add `partitioned` option
+
 0.5.0 / 2022-04-11
 ==================
 
diff --git a/README.md b/README.md
index 5449c3a..a489092 100644
--- a/README.md
+++ b/README.md
@@ -150,6 +150,15 @@ the `Secure` attribute is set, otherwise it is not. By default, the `Secure` att
 **note** be careful when setting this to `true`, as compliant clients will not send the cookie back to
 the server in the future if the browser does not have an HTTPS connection.
 
+##### partitioned
+
+Specifies the `boolean` value for the [`Partitioned` `Set-Cookie`](draft-cutler-httpbis-partitioned-cookies) attribute. When truthy, the `Partitioned` attribute is set, otherwise it is not. By default, the `Partitioned` attribute is not set.
+
+**note** This is an attribute that has not yet been fully standardized, and may change in the future.
+This also means many clients may ignore this attribute until they understand it.
+
+More information about can be found in [the proposal](https://github.com/privacycg/CHIPS).
+
 ## Example
 
 The following example uses this module in conjunction with the Node.js core HTTP server
@@ -286,6 +295,7 @@ $ npm run bench
 [rfc-6265-5.2.5]: https://tools.ietf.org/html/rfc6265#section-5.2.5
 [rfc-6265-5.2.6]: https://tools.ietf.org/html/rfc6265#section-5.2.6
 [rfc-6265-5.3]: https://tools.ietf.org/html/rfc6265#section-5.3
+[draft-cutler-httpbis-partitioned-cookies]: https://datatracker.ietf.org/doc/html/draft-cutler-httpbis-partitioned-cookies/
 
 ## License
 
diff --git a/index.js b/index.js
index 12128b9..fcd0111 100644
--- a/index.js
+++ b/index.js
@@ -214,6 +214,10 @@ function serialize(name, val, options) {
     }
   }
 
+  if (opt.partitioned) {
+    str += '; Partitioned'
+  }
+
   return str;
 }
 
diff --git a/test/serialize.js b/test/serialize.js
index 6e34590..41c3ff5 100644
--- a/test/serialize.js
+++ b/test/serialize.js
@@ -193,4 +193,18 @@ describe('cookie.serialize(name, value, options)', function () {
       assert.equal(cookie.serialize('foo', 'bar', { secure: false }), 'foo=bar')
     })
   })
+
+  describe('with "partitioned" option', function () {
+    it('should include partitioned flag when true', function () {
+      assert.equal(cookie.serialize('foo', 'bar', { partitioned: true }), 'foo=bar; Partitioned')
+    })
+
+    it('should not include partitioned flag when false', function () {
+      assert.equal(cookie.serialize('foo', 'bar', { partitioned: false }), 'foo=bar')
+    })
+
+    it('should not include partitioned flag when not defined', function () {
+      assert.equal(cookie.serialize('foo', 'bar', {}), 'foo=bar')
+    })
+  })
 })