diff --git a/api/client-server/v1/rooms.yaml b/api/client-server/v1/rooms.yaml
index 90b51290..ff5587a9 100644
--- a/api/client-server/v1/rooms.yaml
+++ b/api/client-server/v1/rooms.yaml
@@ -311,7 +311,11 @@ paths:
                     "user_id": "@alice:example.com"
                   }
                 ],
-                "visibility": "private"
+                "visibility": "private",
+                "account_data": [{
+                    "type": "m.tag",
+                    "content": {"tags": {"work": {"order": "1"}}}
+                }]
               }
           schema:
             title: RoomInfo
@@ -371,6 +375,15 @@ paths:
                 description: |-
                   Whether this room is visible to the ``/publicRooms`` API
                   or not."
+              account_data:
+                type: array
+                description: |-
+                  The private data that this user has attached to this room.
+                items:
+                  title: Event
+                  type: object
+                  allOf:
+                    - "$ref": "core-event-schema/event.json"
             required: ["room_id"]
         403:
           description: >
diff --git a/api/client-server/v1/sync.yaml b/api/client-server/v1/sync.yaml
index d07e9399..973ccc6e 100644
--- a/api/client-server/v1/sync.yaml
+++ b/api/client-server/v1/sync.yaml
@@ -245,7 +245,11 @@ paths:
                                   "user_id": "@alice:localhost"
                               }
                           ],
-                          "visibility": "private"
+                          "visibility": "private",
+                          "account_data": [{
+                            "type": "m.tag",
+                            "content": {"tags": {"work": {"order": "1"}}}
+                          }]
                       }
                   ]
               }
@@ -332,6 +336,16 @@ paths:
                       description: |-
                         Whether this room is visible to the ``/publicRooms`` API
                         or not."
+                    account_data:
+                      type: array
+                      description: |-
+                        The private data that this user has attached to
+                        this room.
+                      items:
+                        title: Event
+                        type: object
+                        allOf:
+                          - "$ref": "core-event-schema/event.json"
                   required: ["room_id", "membership"]
             required: ["end", "rooms", "presence"]
         404:
diff --git a/api/client-server/v2_alpha/sync.yaml b/api/client-server/v2_alpha/sync.yaml
index 0c9d6186..6f2f1412 100644
--- a/api/client-server/v2_alpha/sync.yaml
+++ b/api/client-server/v2_alpha/sync.yaml
@@ -132,6 +132,14 @@ paths:
                             e.g. typing.
                           allOf:
                             - $ref: "definitions/event_batch.json"
+                        account_data:
+                          title: Account Data
+                          type: object
+                          description: |-
+                            The private data that this user has attached to
+                            this room.
+                          allOf:
+                          - $ref: "definitions/event_batch.json"
                   invite:
                     title: Invited Rooms
                     type: object
@@ -252,6 +260,14 @@ paths:
                             "content": {"user_ids": ["@alice:example.com"]}
                           }
                         ]
+                      },
+                      "account_data": {
+                        "events": [
+                          {
+                            "type": "m.tag",
+                            "content": {"tags": {"work": {"order": "1"}}}
+                          }
+                        ]
                       }
                     }
                   },
diff --git a/api/client-server/v2_alpha/tags.yaml b/api/client-server/v2_alpha/tags.yaml
new file mode 100644
index 00000000..91945dca
--- /dev/null
+++ b/api/client-server/v2_alpha/tags.yaml
@@ -0,0 +1,147 @@
+swagger: '2.0'
+info:
+  title: "Matrix Client-Server tag API"
+  version: "1.0.0"
+host: localhost:8008
+schemes:
+  - https
+  - http
+basePath: /_matrix/client/v2_alpha
+consumes:
+  - application/json
+produces:
+  - application/json
+securityDefinitions:
+  accessToken:
+    type: apiKey
+    description: The user_id or application service access_token
+    name: access_token
+    in: query
+paths:
+  "/user/{userId}/rooms/{roomId}/tags":
+    get:
+      summary: List the tags for a room.
+      description: |-
+        List the tags set by a user on a room.
+      security:
+        - accessToken: []
+      parameters:
+        - in: path
+          type: string
+          name: userId
+          required: true
+          description: |-
+            The id of the user to get tags for. The access token must be
+            authorized to make requests for this user id.
+          x-example: "@alice:example.com"
+        - in: path
+          type: string
+          name: roomId
+          required: true
+          description: |-
+            The id of the room to get tags for.
+          x-example: "!726s6s6q:example.com"
+      responses:
+        200:
+          description:
+            The list of tags for the user for the room.
+          schema:
+            type: object
+            properties:
+              tags:
+                title: Tags
+                type: object
+          examples:
+            application/json: |-
+              {
+                "tags": {
+                  "work": {"order": "1"},
+                  "pinned": {}
+                }
+              }
+  "/user/{userId}/rooms/{roomId}/tags/{tag}":
+    put:
+      summary: Add a tag to a room.
+      description: |-
+        Add a tag to the room.
+      security:
+        - accessToken: []
+      parameters:
+        - in: path
+          type: string
+          name: userId
+          required: true
+          description: |-
+            The id of the user to add a tag for. The access token must be
+            authorized to make requests for this user id.
+          x-example: "@alice:example.com"
+        - in: path
+          type: string
+          name: roomId
+          required: true
+          description: |-
+            The id of the room to add a tag to.
+          x-example: "!726s6s6q:example.com"
+        - in: path
+          type: string
+          name: tag
+          required: true
+          description: |-
+            The tag to add.
+          x-example: "work"
+        - in: body
+          name: body
+          required: true
+          description: |-
+            Extra data for the tag, e.g. ordering.
+          schema:
+            type: object
+            example: |-
+              {"order": "1"}
+      responses:
+        200:
+          description:
+            The tag was successfully added.
+          schema:
+            type: object
+          examples:
+            application/json: |-
+              {}
+    delete:
+      summary: Remove a tag from the room.
+      description: |-
+        Remove a tag from the room.
+      security:
+        - access_token: []
+      parameters:
+        - in: path
+          type: string
+          name: userId
+          required: true
+          description: |-
+            The id of the user to remove a tag for. The access token must be
+            authorized to make requests for this user id.
+          x-example: "@alice:example.com"
+        - in: path
+          type: string
+          name: roomId
+          required: true
+          description: |-
+            The id of the room to remove a tag from.
+          x-example: "!726s6s6q:example.com"
+        - in: path
+          type: string
+          name: tag
+          required: true
+          description: |-
+            The tag to remove.
+          x-example: "work"
+      responses:
+        200:
+          description:
+            The tag was successfully removed
+          schema:
+            type: object
+          examples:
+            application/json: |-
+              {}
diff --git a/event-schemas/examples/v1/m.tag b/event-schemas/examples/v1/m.tag
new file mode 100644
index 00000000..00e81060
--- /dev/null
+++ b/event-schemas/examples/v1/m.tag
@@ -0,0 +1,8 @@
+{
+  "type": "m.tag",
+  "content": {
+    "tags": {
+      "work": {"order": 1}
+    }
+  }
+}
diff --git a/event-schemas/schema/v1/m.tag b/event-schemas/schema/v1/m.tag
new file mode 100644
index 00000000..4c5b4fa5
--- /dev/null
+++ b/event-schemas/schema/v1/m.tag
@@ -0,0 +1,25 @@
+{
+  "type": "object",
+  "title": "Tag Event",
+  "description": "Informs the client of tags on a room.",
+  "properties": {
+    "type": {
+      "type": "string",
+      "enum": ["m.tag"]
+    },
+    "content": {
+      "type": "object",
+      "properties": {
+        "tags": {
+          "type": "object",
+          "description": "The tags on the room and their contents.",
+          "additionalProperties": {
+            "title": "Tag",
+            "type": "object"
+          }
+        }
+      }
+    }
+  },
+  "required": ["type", "content"]
+}
diff --git a/specification/modules/tags.rst b/specification/modules/tags.rst
new file mode 100644
index 00000000..bb467bc0
--- /dev/null
+++ b/specification/modules/tags.rst
@@ -0,0 +1,48 @@
+Room Tagging
+============
+
+.. _module:tagging:
+
+Users can add tags to rooms. Tags are short strings used to label rooms, e.g.
+"work", "family". A room may have multiple tags. Tags are only visible to the
+user that set them but are shared across all their devices.
+
+Events
+------
+
+The tags on a room are received as single ``m.tag`` event in the
+``account_data`` section of a room in a v2 /sync.
+
+The ``m.tag`` can also be received in a v1 /events response or in the
+``account_data`` section of a room in v1 /initialSync. ``m.tag``
+events appearing in v1 /events will have a ``room_id`` with the room
+the tags are for.
+
+Each tag has an associated JSON object with information about the tag, e.g how
+to order the rooms with a given tag.
+
+Ordering information is given under the ``order`` key as a string. The string
+are compared lexicographically by unicode codepoint to determine which should
+displayed first. So a room with a tag with an ``order`` key of ``"apples"``
+would appear before a room with a tag with an ``order`` key of ``"oranges"``.
+If a room has a tag without an ``order`` key then it should appear after the
+rooms with that tag that have an ``order`` key.
+
+The name of a tag MUST not exceed 255 bytes.
+
+The name of a tag should be human readable. When displaying tags for a room a
+client should display this human readable name. When adding a tag for a room
+a client may offer a list to choose from that includes all the tags that the
+user has previously set on any of their rooms.
+
+Two special names are listed in the specification:
+
+* ``m.favourite``
+* ``m.lowpriority``
+
+{{m_tag_event}}
+
+Client Behaviour
+----------------
+
+{{v2_tags_http_api}}
diff --git a/specification/targets.yaml b/specification/targets.yaml
index 8e6a2ce0..caae953f 100644
--- a/specification/targets.yaml
+++ b/specification/targets.yaml
@@ -26,6 +26,7 @@ groups:  # reusable blobs of files when prefixed with 'group:'
     - modules/third_party_invites.rst
     - modules/search.rst
     - modules/guest_access.rst
+    - modules/tags.rst
 
 
 title_styles: ["=", "-", "~", "+", "^", "`"]