diff --git a/changelog.d/18052.removal b/changelog.d/18052.removal
new file mode 100644
index 0000000000000000000000000000000000000000..f173b9ba4d7bd49c49b659fc18b8667e68139b25
--- /dev/null
+++ b/changelog.d/18052.removal
@@ -0,0 +1 @@
+Remove the unstable [MSC4151](https://github.com/matrix-org/matrix-spec-proposals/pull/4151) implementation. The stable support remains, per [Matrix 1.13](https://spec.matrix.org/v1.13/client-server-api/#post_matrixclientv3roomsroomidreport).
\ No newline at end of file
diff --git a/synapse/config/experimental.py b/synapse/config/experimental.py
index eb8d967e70901d14e4f67f313f082f3e05b968e8..90d19849ffd0ac61d0607a17cce318889bbfd1b3 100644
--- a/synapse/config/experimental.py
+++ b/synapse/config/experimental.py
@@ -436,9 +436,6 @@ class ExperimentalConfig(Config):
                 ("experimental", "msc4108_delegation_endpoint"),
             )
 
-        # MSC4151: Report room API (Client-Server API)
-        self.msc4151_enabled: bool = experimental.get("msc4151_enabled", False)
-
         # MSC4210: Remove legacy mentions
         self.msc4210_enabled: bool = experimental.get("msc4210_enabled", False)
 
diff --git a/synapse/rest/client/reporting.py b/synapse/rest/client/reporting.py
index 949f077035182fee1c852a83932e882000d91a58..c5037be8b7565f1d15ee730b9366da74e7b1f39a 100644
--- a/synapse/rest/client/reporting.py
+++ b/synapse/rest/client/reporting.py
@@ -20,13 +20,11 @@
 #
 
 import logging
-import re
 from http import HTTPStatus
 from typing import TYPE_CHECKING, Tuple
 
 from synapse._pydantic_compat import StrictStr
 from synapse.api.errors import AuthError, Codes, NotFoundError, SynapseError
-from synapse.api.urls import CLIENT_API_PREFIX
 from synapse.http.server import HttpServer
 from synapse.http.servlet import (
     RestServlet,
@@ -127,16 +125,6 @@ class ReportRoomRestServlet(RestServlet):
         self.clock = hs.get_clock()
         self.store = hs.get_datastores().main
 
-        # TODO: Remove the unstable variant after 2-3 releases
-        # https://github.com/element-hq/synapse/issues/17373
-        if hs.config.experimental.msc4151_enabled:
-            self.PATTERNS.append(
-                re.compile(
-                    f"^{CLIENT_API_PREFIX}/unstable/org.matrix.msc4151"
-                    "/rooms/(?P<room_id>[^/]*)/report$"
-                )
-            )
-
     class PostBody(RequestBodyModel):
         reason: StrictStr
 
diff --git a/synapse/rest/client/versions.py b/synapse/rest/client/versions.py
index ba1141bbe597a96e8e34572a7ce625523dfddd91..a1d089ebac8c50f7e29777cf8a19bfa1fbbb7a63 100644
--- a/synapse/rest/client/versions.py
+++ b/synapse/rest/client/versions.py
@@ -170,8 +170,6 @@ class VersionsRestServlet(RestServlet):
                     ),
                     # MSC4140: Delayed events
                     "org.matrix.msc4140": bool(self.config.server.max_event_delay_ms),
-                    # MSC4151: Report room API (Client-Server API)
-                    "org.matrix.msc4151": self.config.experimental.msc4151_enabled,
                     # Simplified sliding sync
                     "org.matrix.simplified_msc3575": msc3575_enabled,
                 },