diff --git a/src/@types/event.ts b/src/@types/event.ts
index fd906266e..1416a0b71 100644
--- a/src/@types/event.ts
+++ b/src/@types/event.ts
@@ -53,6 +53,7 @@ import {
 } from "../webrtc/callEventTypes.ts";
 import {
     type IRTCNotificationContent,
+    type IRTCDeclineContent,
     type EncryptionKeysEventContent,
     type ICallNotifyContent,
 } from "../matrixrtc/types.ts";
@@ -152,6 +153,7 @@ export enum EventType {
     // MatrixRTC events
     CallNotify = "org.matrix.msc4075.call.notify",
     RTCNotification = "org.matrix.msc4075.rtc.notification",
+    RTCDecline = "org.matrix.msc4310.rtc.decline",
 }
 
 export enum RelationType {
@@ -332,6 +334,7 @@ export interface TimelineEvents {
     [EventType.CallEncryptionKeysPrefix]: EncryptionKeysEventContent;
     [EventType.CallNotify]: ICallNotifyContent;
     [EventType.RTCNotification]: IRTCNotificationContent;
+    [EventType.RTCDecline]: IRTCDeclineContent;
     [M_BEACON.name]: MBeaconEventContent;
     [M_POLL_START.name]: PollStartEventContent;
     [M_POLL_END.name]: PollEndEventContent;
diff --git a/src/client.ts b/src/client.ts
index f30b9ca0b..07cf8547c 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -3589,6 +3589,12 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
         return await this.setRoomReadMarkersHttpRequest(roomId, rmEventId, rrEventId, rpEventId);
     }
 
+    public sendRtcDecline(roomId: string, notificationEventId: string): Promise<ISendEventResponse> {
+        return this.sendEvent(roomId, EventType.RTCDecline, {
+            "m.relates_to": { event_id: notificationEventId, rel_type: RelationType.Reference },
+        });
+    }
+
     /**
      * Get a preview of the given URL as of (roughly) the given point in time,
      * described as an object with OpenGraph keys and associated values.
diff --git a/src/matrixrtc/types.ts b/src/matrixrtc/types.ts
index 73c5a0170..1f7bbe3a6 100644
--- a/src/matrixrtc/types.ts
+++ b/src/matrixrtc/types.ts
@@ -104,6 +104,12 @@ export interface IRTCNotificationContent extends RelationEvent {
     "lifetime": number;
 }
 
+/**
+ * MSC4310 decline event content for `org.matrix.msc4310.rtc.decline`.
+ * Sent as a standard m.reference relation to an `org.matrix.msc4075.rtc.notification` event.
+ */
+export interface IRTCDeclineContent extends RelationEvent {}
+
 export enum Status {
     Disconnected = "Disconnected",
     Connecting = "Connecting",