diff --git a/spec/unit/content-helpers.spec.ts b/spec/unit/content-helpers.spec.ts
index 71b7344ed6a..ba431d9d586 100644
--- a/spec/unit/content-helpers.spec.ts
+++ b/spec/unit/content-helpers.spec.ts
@@ -17,7 +17,13 @@ limitations under the License.
 import { REFERENCE_RELATION } from "matrix-events-sdk";
 
 import { LocationAssetType, M_ASSET, M_LOCATION, M_TIMESTAMP } from "../../src/@types/location";
-import { makeBeaconContent, makeBeaconInfoContent } from "../../src/content-helpers";
+import { M_TOPIC } from "../../src/@types/topic";
+import {
+    makeBeaconContent,
+    makeBeaconInfoContent,
+    makeTopicContent,
+    parseTopicContent,
+} from "../../src/content-helpers";
 
 describe('Beacon content helpers', () => {
     describe('makeBeaconInfoContent()', () => {
@@ -122,3 +128,68 @@ describe('Beacon content helpers', () => {
         });
     });
 });
+
+describe('Topic content helpers', () => {
+    describe('makeTopicContent()', () => {
+        it('creates fully defined event content without html', () => {
+            expect(makeTopicContent("pizza")).toEqual({
+                topic: "pizza",
+                [M_TOPIC.name]: [{
+                    body: "pizza",
+                    mimetype: "text/plain",
+                }],
+            });
+        });
+
+        it('creates fully defined event content with html', () => {
+            expect(makeTopicContent("pizza", "<b>pizza</b>")).toEqual({
+                topic: "pizza",
+                [M_TOPIC.name]: [{
+                    body: "pizza",
+                    mimetype: "text/plain",
+                }, {
+                    body: "<b>pizza</b>",
+                    mimetype: "text/html",
+                }],
+            });
+        });
+    });
+
+    describe('parseTopicContent()', () => {
+        it('parses event content with plain text topic without mimetype', () => {
+            expect(parseTopicContent({
+                topic: "pizza",
+                [M_TOPIC.name]: [{
+                    body: "pizza",
+                }],
+            })).toEqual({
+                text: "pizza",
+            });
+        });
+
+        it('parses event content with plain text topic', () => {
+            expect(parseTopicContent({
+                topic: "pizza",
+                [M_TOPIC.name]: [{
+                    body: "pizza",
+                    mimetype: "text/plain",
+                }],
+            })).toEqual({
+                text: "pizza",
+            });
+        });
+
+        it('parses event content with html topic', () => {
+            expect(parseTopicContent({
+                topic: "pizza",
+                [M_TOPIC.name]: [{
+                    body: "<b>pizza</b>",
+                    mimetype: "text/html",
+                }],
+            })).toEqual({
+                text: "pizza",
+                html: "<b>pizza</b>",
+            });
+        });
+    });
+});
diff --git a/spec/unit/matrix-client.spec.ts b/spec/unit/matrix-client.spec.ts
index d1562d766cc..489aa167950 100644
--- a/spec/unit/matrix-client.spec.ts
+++ b/spec/unit/matrix-client.spec.ts
@@ -33,7 +33,7 @@ import { ReceiptType } from "../../src/@types/read_receipts";
 import * as testUtils from "../test-utils/test-utils";
 import { makeBeaconInfoContent } from "../../src/content-helpers";
 import { M_BEACON_INFO } from "../../src/@types/beacon";
-import { Room } from "../../src";
+import { ContentHelpers, Room } from "../../src";
 import { makeBeaconEvent } from "../test-utils/beacon";
 
 jest.useFakeTimers();
@@ -1104,6 +1104,41 @@ describe("MatrixClient", function() {
         });
     });
 
+    describe("setRoomTopic", () => {
+        const roomId = "!foofoofoofoofoofoo:matrix.org";
+        const createSendStateEventMock = (topic: string, htmlTopic?: string) => {
+            return jest.fn()
+                .mockImplementation((roomId: string, eventType: string, content: any, stateKey: string) => {
+                    expect(roomId).toEqual(roomId);
+                    expect(eventType).toEqual(EventType.RoomTopic);
+                    expect(content).toMatchObject(ContentHelpers.makeTopicContent(topic, htmlTopic));
+                    expect(stateKey).toBeUndefined();
+                    return Promise.resolve();
+                });
+        };
+
+        it("is called with plain text topic and sends state event", async () => {
+            const sendStateEvent = createSendStateEventMock("pizza");
+            client.sendStateEvent = sendStateEvent;
+            await client.setRoomTopic(roomId, "pizza");
+            expect(sendStateEvent).toHaveBeenCalledTimes(1);
+        });
+
+        it("is called with plain text topic and callback and sends state event", async () => {
+            const sendStateEvent = createSendStateEventMock("pizza");
+            client.sendStateEvent = sendStateEvent;
+            await client.setRoomTopic(roomId, "pizza", () => {});
+            expect(sendStateEvent).toHaveBeenCalledTimes(1);
+        });
+
+        it("is called with plain text and HTML topic and sends state event", async () => {
+            const sendStateEvent = createSendStateEventMock("pizza", "<b>pizza</b>");
+            client.sendStateEvent = sendStateEvent;
+            await client.setRoomTopic(roomId, "pizza", "<b>pizza</b>");
+            expect(sendStateEvent).toHaveBeenCalledTimes(1);
+        });
+    });
+
     describe("setPassword", () => {
         const auth = { session: 'abcdef', type: 'foo' };
         const newPassword = 'newpassword';
diff --git a/src/@types/topic.ts b/src/@types/topic.ts
new file mode 100644
index 00000000000..0d2708b2e50
--- /dev/null
+++ b/src/@types/topic.ts
@@ -0,0 +1,62 @@
+/*
+Copyright 2022 The Matrix.org Foundation C.I.C.
+
+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.
+*/
+
+import { EitherAnd, IMessageRendering } from "matrix-events-sdk";
+
+import { UnstableValue } from "../NamespacedValue";
+
+/**
+ * Extensible topic event type based on MSC3765
+ * https://github.com/matrix-org/matrix-spec-proposals/pull/3765
+ */
+
+/**
+ * Eg
+ * {
+ *      "type": "m.room.topic,
+ *      "state_key": "",
+ *      "content": {
+ *          "topic": "All about **pizza**",
+ *          "m.topic": [{
+ *              "body": "All about **pizza**",
+ *              "mimetype": "text/plain",
+ *          }, {
+ *              "body": "All about <b>pizza</b>",
+ *              "mimetype": "text/html",
+ *          }],
+ *      }
+ * }
+ */
+
+/**
+ * The event type for an m.topic event (in content)
+ */
+export const M_TOPIC = new UnstableValue("m.topic", "org.matrix.msc3765.topic");
+
+/**
+ * The event content for an m.topic event (in content)
+ */
+export type MTopicContent = IMessageRendering[];
+
+/**
+ * The event definition for an m.topic event (in content)
+ */
+export type MTopicEvent = EitherAnd<{ [M_TOPIC.name]: MTopicContent }, { [M_TOPIC.altName]: MTopicContent }>;
+
+/**
+ * The event content for an m.room.topic event
+ */
+export type MRoomTopicEventContent = { topic: string } & MTopicEvent;
diff --git a/src/client.ts b/src/client.ts
index bb7b9e96e6a..5187a13b0d6 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -3557,12 +3557,31 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
     /**
      * @param {string} roomId
      * @param {string} topic
+     * @param {string} htmlTopic Optional.
      * @param {module:client.callback} callback Optional.
      * @return {Promise} Resolves: TODO
      * @return {module:http-api.MatrixError} Rejects: with an error response.
      */
-    public setRoomTopic(roomId: string, topic: string, callback?: Callback): Promise<ISendEventResponse> {
-        return this.sendStateEvent(roomId, EventType.RoomTopic, { topic: topic }, undefined, callback);
+    public setRoomTopic(
+        roomId: string,
+        topic: string,
+        htmlTopic?: string,
+    ): Promise<ISendEventResponse>;
+    public setRoomTopic(
+        roomId: string,
+        topic: string,
+        callback?: Callback,
+    ): Promise<ISendEventResponse>;
+    public setRoomTopic(
+        roomId: string,
+        topic: string,
+        htmlTopicOrCallback?: string | Callback,
+    ): Promise<ISendEventResponse> {
+        const isCallback = typeof htmlTopicOrCallback === 'function';
+        const htmlTopic = isCallback ? undefined : htmlTopicOrCallback;
+        const callback = isCallback ? htmlTopicOrCallback : undefined;
+        const content = ContentHelpers.makeTopicContent(topic, htmlTopic);
+        return this.sendStateEvent(roomId, EventType.RoomTopic, content, undefined, callback);
     }
 
     /**
diff --git a/src/content-helpers.ts b/src/content-helpers.ts
index 383b9b34396..8c813b7aad6 100644
--- a/src/content-helpers.ts
+++ b/src/content-helpers.ts
@@ -16,7 +16,7 @@ limitations under the License.
 
 /** @module ContentHelpers */
 
-import { REFERENCE_RELATION } from "matrix-events-sdk";
+import { isProvided, REFERENCE_RELATION } from "matrix-events-sdk";
 
 import { MBeaconEventContent, MBeaconInfoContent, MBeaconInfoEventContent } from "./@types/beacon";
 import { MsgType } from "./@types/event";
@@ -32,6 +32,7 @@ import {
     MAssetContent,
     LegacyLocationEventContent,
 } from "./@types/location";
+import { MRoomTopicEventContent, MTopicContent, M_TOPIC } from "./@types/topic";
 
 /**
  * Generates the content for a HTML Message event
@@ -190,6 +191,34 @@ export const parseLocationEvent = (wireEventContent: LocationEventWireContent):
     return makeLocationContent(fallbackText, geoUri, timestamp, description, assetType);
 };
 
+/**
+ * Topic event helpers
+ */
+export type MakeTopicContent = (
+    topic: string,
+    htmlTopic?: string,
+) => MRoomTopicEventContent;
+
+export const makeTopicContent: MakeTopicContent = (topic, htmlTopic) => {
+    const renderings = [{ body: topic, mimetype: "text/plain" }];
+    if (isProvided(htmlTopic)) {
+        renderings.push({ body: htmlTopic, mimetype: "text/html" });
+    }
+    return { topic, [M_TOPIC.name]: renderings };
+};
+
+export type TopicState = {
+    text: string;
+    html?: string;
+};
+
+export const parseTopicContent = (content: MRoomTopicEventContent): TopicState => {
+    const mtopic = M_TOPIC.findIn<MTopicContent>(content);
+    const text = mtopic?.find(r => !isProvided(r.mimetype) || r.mimetype === "text/plain")?.body ?? content.topic;
+    const html = mtopic?.find(r => r.mimetype === "text/html")?.body;
+    return { text, html };
+};
+
 /**
  * Beacon event helpers
  */