diff --git a/api/client-server/account-data.yaml b/api/client-server/account-data.yaml
index 76b2b156..c468f1c0 100644
--- a/api/client-server/account-data.yaml
+++ b/api/client-server/account-data.yaml
@@ -67,6 +67,17 @@ paths:
         200:
           description:
             The account_data was successfully added.
+        405:
+          description:
+            The account data event type cannot be set here. This generally indicates
+            that another API is available for managing the data contained in the event.
+          schema:
+            $ref: "definitions/errors/error.yaml"
+          examples: 
+            application/json: {
+              "errcode": "M_UNKNOWN",
+              "error": "Cannot set m.fully_read through this API. Use /rooms/{roomId}/read_markers"
+            }
       tags:
         - User data
   "/user/{userId}/rooms/{roomId}/account_data/{type}":
@@ -116,5 +127,16 @@ paths:
         200:
           description:
             The account_data was successfully added.
+        405:
+          description:
+            The account data event type cannot be set here. This generally indicates
+            that another API is available for managing the data contained in the event.
+          schema:
+            $ref: "definitions/errors/error.yaml"
+          examples: 
+            application/json: {
+              "errcode": "M_UNKNOWN",
+              "error": "Cannot set m.fully_read through this API. Use /rooms/{roomId}/read_markers"
+            }
       tags:
         - User data
diff --git a/api/client-server/read_markers.yaml b/api/client-server/read_markers.yaml
new file mode 100644
index 00000000..a74592c5
--- /dev/null
+++ b/api/client-server/read_markers.yaml
@@ -0,0 +1,79 @@
+# Copyright 2018 New Vector Ltd
+#
+# 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 Read Marker API"
+  version: "1.0.0"
+host: localhost:8008
+schemes:
+  - https
+  - http
+basePath: /_matrix/client/%CLIENT_MAJOR_VERSION%
+consumes:
+  - application/json
+produces:
+  - application/json
+securityDefinitions:
+  $ref: definitions/security.yaml
+paths:
+  "/rooms/{roomId}/read_markers":
+    post:
+      summary: Set the position of the read marker for a room.
+      description: |-
+        Sets the position of the read marker for a given room, and optionally
+        the read receipt's location.
+      operationId: setReadMarker
+      security:
+        - accessToken: []
+      parameters:
+        - in: path
+          type: string
+          name: roomId
+          description: The room ID to set the read marker in for the user.
+          required: true
+          x-example: "!somewhere:domain.com"
+        - in: body
+          name: body
+          description: The read marker and optional read receipt locations.
+          required: true
+          schema:
+            type: object
+            properties:
+              "m.fully_read":
+                type: string
+                description: |-
+                  The event ID the read marker should be located at. The
+                  event MUST belong to the room.
+                example: "$somewhere:domain.com"
+              "m.read":
+                type: string
+                description: |-
+                  The event ID to set the read receipt location at. This is
+                  equivalent to calling ``/receipt/m.read/$elsewhere:domain.com``
+                  and is provided here to save that extra call.
+                example: "$elsewhere:domain.com"
+            required: ['m.fully_read']
+      responses:
+        200:
+          description: |-
+            The read marker, and read receipt if provided, have been updated.
+          schema:
+            type: object
+            properties: {}
+        429:
+          description: This request was rate-limited.
+          schema:
+            "$ref": "definitions/errors/rate_limited.yaml"
+      tags:
+        - Read Markers
diff --git a/event-schemas/examples/m.fully_read b/event-schemas/examples/m.fully_read
new file mode 100644
index 00000000..8278c6fa
--- /dev/null
+++ b/event-schemas/examples/m.fully_read
@@ -0,0 +1,8 @@
+{
+  "$ref": "core/event.json",
+  "type": "m.fully_read",
+  "room_id": "!somewhere:domain.com",
+  "content": {
+    "event_id": "$someplace:domain.com"
+  }
+}
diff --git a/event-schemas/schema/m.fully_read b/event-schemas/schema/m.fully_read
new file mode 100644
index 00000000..51a1942f
--- /dev/null
+++ b/event-schemas/schema/m.fully_read
@@ -0,0 +1,29 @@
+{
+    "type": "object",
+    "title": "Read Marker Location Event",
+    "description": "The current location of the user's read marker in a room. This event appears in the user's room account data for the room the marker is applicable for.",
+    "allOf": [{
+        "$ref": "core-event-schema/event.yaml"
+    }],
+    "properties": {
+        "content": {
+            "type": "object",
+            "properties": {
+                "event_id": {
+                    "type": "string",
+                    "description": "The event the user's read marker is located at in the room."
+                }
+            },
+            "required": ["event_id"]
+        },
+        "type": {
+            "type": "string",
+            "enum": ["m.fully_read"]
+        },
+        "room_id": {
+            "type": "string",
+            "description": "The room ID the read marker applies to."
+        }
+    },
+    "required": ["type", "room_id", "content"]
+}
diff --git a/specification/modules/read_markers.rst b/specification/modules/read_markers.rst
new file mode 100644
index 00000000..0a5578d6
--- /dev/null
+++ b/specification/modules/read_markers.rst
@@ -0,0 +1,70 @@
+.. Copyright 2018 New Vector Ltd
+..
+.. 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.
+
+Read Markers
+============
+
+.. _module:read-markers:
+
+A "read marker" is a bookmark in the room's history where the user has last
+read a message. Read receipts cover the most recently read message, and have
+slightly different semantics where they are to be sent when the user has most
+likely seen the message, but not necessarily read it. A read marker tracks
+the user's last read message, therefore making the messages between the read
+marker and read receipt "potentially read" and messages before the read marker
+as "read". Messages after the read receipt should be considered as "unread",
+therefore the read marker should always be earlier or equal to the location of
+the read receipt.
+
+Events
+------
+The user's read marker is kept as an event in the room's `account data`_. The
+event may be read to determine the user's current read marker location in the
+room, and just like other account data events the event will be pushed down
+the event stream when updated.
+
+The read marker is kept under an ``m.fully_read`` event. If the event does
+not exist on the user's account data, the read marker should be considered
+to be the user's read receipt location.
+
+{{m_fully_read_event}}
+
+Client behaviour
+----------------
+The client cannot update read markers by directly modifying the ``m.fully_read``
+account data event. Instead, the client must make use of the read markers API
+to change the values.
+
+The read markers API can additionally update the user's read receipt (``m.read``)
+location in the same operation as setting the read marker location. This is
+because read receipts and read markers are commonly updated at the same time,
+and therefore the client might wish to save an extra HTTP call. Providing an
+``m.read`` location performs the same task as a request to ``/receipts/m.read/$event:domain.com``.
+
+{{read_markers_cs_http_api}}
+
+Server behaviour
+----------------
+The server MUST prevent clients from setting ``m.fully_read`` directly in
+room account data. The server must additionally ensure that it treats the
+presence of ``m.read`` in the ``/read_markers`` request the same as how it
+would for a request to ``/receipts/m.read/$event:domain.com``.
+
+Upon updating the ``m.fully_read`` event due to a request to ``/read_markers``,
+the server MUST send the updated account data event through to the client via
+the event stream (eg: ``/sync``), provided any applicable filters are also
+satisfied.
+
+
+.. _`account data`: #client-config
diff --git a/specification/targets.yaml b/specification/targets.yaml
index 56e9ec34..a2eb5cdd 100644
--- a/specification/targets.yaml
+++ b/specification/targets.yaml
@@ -45,6 +45,7 @@ groups:  # reusable blobs of files when prefixed with 'group:'
     - modules/voip_events.rst
     - modules/typing_notifications.rst
     - modules/receipts.rst
+    - modules/read_markers.rst
     - modules/presence.rst
     - modules/content_repo.rst
     - modules/send_to_device.rst