diff --git a/api/identity/lookup.yaml b/api/identity/lookup.yaml
index d039f2b5..7cd7fded 100644
--- a/api/identity/lookup.yaml
+++ b/api/identity/lookup.yaml
@@ -85,3 +85,56 @@ paths:
               signatures:
                 type: object
                 description: The signatures of the verifying identity services which show that the association should be trusted, if you trust the verifying identity services.
+  "/bulk_lookup":
+    post:
+      summary: Lookup Matrix user IDs for a list of 3pids.
+      description: Lookup Matrix user IDs for a list of 3pids.
+      parameters:
+        - in: body
+          name: body
+          schema:
+            type: object
+            example: {
+              "threepids":
+              [
+                ["email","user@example.org"],
+                ["msisdn", "123456789"],
+                ["email","user2@example.org"]
+              ]
+            }
+            properties:
+              threepids:
+                type: array
+                items:
+                  type: array
+                  title: 3PID mappings
+                  items:
+                    type: string
+                    title: 3PID medium or address
+                description: an array of arrays containing the `3PID Types`_ with the ``medium`` in first position and the ``address`` in second position.
+            required:
+              - "threepids"
+      responses:
+        200:
+          description: A list of known 3PID mappings for the supplied 3PIDs.
+          examples:
+            application/json: {
+              "threepids": [
+                ["email","user@example.org", "@bla:example.org"],
+                ["msisdn", "123456789", "@blah2:example.com"]
+              ]
+            }
+          schema:
+            type: object
+            properties:
+              threepids:
+                type: array
+                items:
+                  type: array
+                  title: 3PID mappings
+                  items:
+                    type: string
+                    title: 3PID medium or address or the Matrix ID
+                description: an array of array containing the `3PID Types`_ with the ``medium`` in first position, the ``address`` in second position and Matrix ID in third position.
+            required:
+              - "threepids"