diff --git a/api/client-server/old_sync.yaml b/api/client-server/old_sync.yaml
index 2e2a629e..c51023ae 100644
--- a/api/client-server/old_sync.yaml
+++ b/api/client-server/old_sync.yaml
@@ -89,6 +89,7 @@ paths:
           description: "Bad pagination ``from`` parameter."
       tags:
         - Room participation
+      deprecated: true
   "/initialSync":
     get:
       summary: Get the user's current state.
@@ -369,6 +370,7 @@ paths:
           description: There is no avatar URL for this user or this user does not exist.
       tags:
         - Room participation
+      deprecated: true
   "/events/{eventId}":
     get:
       summary: Get a single event by event ID.
@@ -406,3 +408,4 @@ paths:
           description: The event was not found or you do not have permission to read this event.
       tags:
         - Room participation
+      deprecated: true
diff --git a/api/client-server/rooms.yaml b/api/client-server/rooms.yaml
index c21bd5b6..0af8316d 100644
--- a/api/client-server/rooms.yaml
+++ b/api/client-server/rooms.yaml
@@ -432,6 +432,7 @@ paths:
             member of the room.
       tags:
         - Room participation
+      deprecated: true
   "/rooms/{roomId}/members":
     get:
       summary: Get the m.room.member events for the room.
diff --git a/templating/matrix_templates/templates/http-api.tmpl b/templating/matrix_templates/templates/http-api.tmpl
index 1253e66e..aa52de33 100644
--- a/templating/matrix_templates/templates/http-api.tmpl
+++ b/templating/matrix_templates/templates/http-api.tmpl
@@ -2,6 +2,11 @@
 
 ``{{endpoint.method}} {{endpoint.path}}``
 {{(5 + (endpoint.path | length) + (endpoint.method | length)) * title_kind}}
+{% if "deprecated" in endpoint and endpoint.deprecated -%}
+.. WARNING::
+  This API is deprecated and will be removed from a future release.
+
+{% endif -%}
 {% if "alias_for_path" in endpoint -%}
 ``{{endpoint.path}}`` is an alias for `{{endpoint.alias_for_path}}`_.
 
diff --git a/templating/matrix_templates/units.py b/templating/matrix_templates/units.py
index f3f7c9d7..a76c7e16 100644
--- a/templating/matrix_templates/units.py
+++ b/templating/matrix_templates/units.py
@@ -269,6 +269,7 @@ class MatrixUnits(Units):
                 full_path = api.get("basePath", "").rstrip("/") + path
                 endpoint = {
                     "title": single_api.get("summary", ""),
+                    "deprecated": single_api.get("deprecated", False),
                     "desc": single_api.get("description", single_api.get("summary", "")),
                     "method": method.upper(),
                     "path": full_path.strip(),