diff --git a/api/client-server/whoami.yaml b/api/client-server/whoami.yaml
new file mode 100644
index 00000000000..4d9d6ceb4fc
--- /dev/null
+++ b/api/client-server/whoami.yaml
@@ -0,0 +1,52 @@
+# Copyright 2017 Travis Ralston
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+swagger: '2.0'
+info:
+  title: "Matrix Client-Server Account Identification API"
+  version: "1.0.0"
+host: localhost:8008
+schemes:
+  - https
+  - http
+basePath: /_matrix/client/%CLIENT_MAJOR_VERSION%
+produces:
+  - application/json
+securityDefinitions:
+  $ref: definitions/security.yaml
+paths:
+  "/account/whoami":
+    get:
+      summary: Gets information about the owner of an access token.
+      description: |-
+        Gets information about the owner of a given access token.
+      security:
+        - accessToken: []
+      parameters: []
+      responses:
+        200:
+          description:
+            The token belongs to a known user.
+          examples:
+            application/json: {
+                "user_id": "@joe:example.org"
+              }
+          schema:
+            type: object
+            required: ["user_id"]
+            properties:
+              user_id:
+                type: string
+                description: The user id that owns the access token.
+      tags:
+        - User data
diff --git a/changelogs/client_server.rst b/changelogs/client_server.rst
index c24f9ef44e7..10387c560e7 100644
--- a/changelogs/client_server.rst
+++ b/changelogs/client_server.rst
@@ -60,6 +60,9 @@
     - ``GET /rooms/{roomId}/joined_members``
       (`#999 <https://github.com/matrix-org/matrix-doc/pull/999>`_).
 
+    - ``GET /account/whoami``
+      (`#1063 <https://github.com/matrix-org/matrix-doc/pull/1063>`_).
+
 - Spec clarifications:
 
   - Add endpoints and logic for invites and third-party invites to the federation
diff --git a/specification/client_server_api.rst b/specification/client_server_api.rst
index 87e90150a93..09f73bb944a 100644
--- a/specification/client_server_api.rst
+++ b/specification/client_server_api.rst
@@ -786,6 +786,11 @@ This is independent of any information kept by any Identity Servers.
 
 {{administrative_contact_cs_http_api}}
 
+Current account information
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+{{whoami_cs_http_api}}
+
 Pagination
 ----------