diff --git a/changelog.d/1821.feature b/changelog.d/1821.feature
new file mode 100644
index 000000000..515408f2a
--- /dev/null
+++ b/changelog.d/1821.feature
@@ -0,0 +1 @@
+Initial support for bridging bans to IRC.
diff --git a/spec/integ/kicking.spec.js b/spec/integ/kicking.spec.js
index 56aa31ea9..f3ec39098 100644
--- a/spec/integ/kicking.spec.js
+++ b/spec/integ/kicking.spec.js
@@ -176,6 +176,118 @@ describe("Kicking", () => {
 });
 
 
+describe("Banning", () => {
+
+    const {env, config, test} = envBundle();
+
+    const mxUser = {
+        id: "@flibble:wibble",
+        nick: "M-flibble"
+    };
+
+    const ircUser = {
+        nick: "bob",
+        localpart: config._server + "_bob",
+        id: `@${config._server}_bob:${config.homeserver.domain}`
+    };
+
+    const ircUserKicker = {
+        nick: "KickerNick",
+        localpart: config._server + "_KickerNick",
+        id: "@" + config._server + "_KickerNick:" + config.homeserver.domain
+    };
+
+    beforeEach(async () => {
+        await test.beforeEach(env);
+
+        // accept connection requests from eeeeeeeeveryone!
+        env.ircMock._autoConnectNetworks(
+            config._server, mxUser.nick, config._server
+        );
+        env.ircMock._autoConnectNetworks(
+            config._server, ircUser.nick, config._server
+        );
+        env.ircMock._autoConnectNetworks(
+            config._server, config._botnick, config._server
+        );
+        // accept join requests from eeeeeeeeveryone!
+        env.ircMock._autoJoinChannels(
+            config._server, mxUser.nick, config._chan
+        );
+        env.ircMock._autoJoinChannels(
+            config._server, ircUser.nick, config._chan
+        );
+        env.ircMock._autoJoinChannels(
+            config._server, config._botnick, config._chan
+        );
+
+        // we also don't care about registration requests for the irc user
+        env.clientMock._intent(ircUser.id)._onHttpRegister({
+            expectLocalpart: ircUser.localpart,
+            returnUserId: ircUser.id
+        });
+
+        await test.initEnv(env);
+
+        // make the matrix user be on IRC
+        await env.mockAppService._trigger("type:m.room.message", {
+            content: {
+                body: "let me in",
+                msgtype: "m.text"
+            },
+            user_id: mxUser.id,
+            room_id: config._roomid,
+            type: "m.room.message"
+        });
+        const botIrcClient = await env.ircMock._findClientAsync(config._server, config._botnick);
+        // make the IRC user be on Matrix
+        botIrcClient.emit("message", ircUser.nick, config._chan, "let me in");
+    });
+
+    afterEach(async () => test.afterEach(env));
+
+    describe("IRC users on Matrix", () => {
+        it("should make the virtual IRC client set MODE +b and KICK the real IRC user", async () => {
+            let reason = "Get some help.";
+            let userBannedPromise = new Promise(function(resolve, reject) {
+                env.ircMock._whenClient(config._server, mxUser.nick, "send",
+                function(client, cmd, chan, arg1, arg2) {
+                    expect(client.nick).toEqual(mxUser.nick);
+                    expect(client.addr).toEqual(config._server);
+                    expect(chan).toEqual(config._chan);
+                    if (cmd !== "KICK") {
+                        // We sent a MODE
+                        expect(cmd).toEqual("MODE");
+                        expect(arg1).toEqual("+b"); // mode +b => ban
+                        expect(arg2).toEqual(`${ircUser.nick}!*@*`); // argument to +b
+                    }
+                    else {
+                        expect(cmd).toEqual("KICK");
+                        expect(arg1).toEqual(ircUser.nick); // nick
+                        expect(arg2.indexOf(reason)).not.toEqual(-1, // kick reason
+                            `kick reason was not mirrored to IRC. Got '${arg2}',
+                            expected '${reason}'.`);
+                    }
+                    resolve();
+                });
+            });
+
+            await env.mockAppService._trigger("type:m.room.member", {
+                content: {
+                    reason: reason,
+                    membership: "ban"
+                },
+                user_id: mxUser.id,
+                state_key: ircUser.id,
+                room_id: config._roomid,
+                type: "m.room.member"
+            });
+            await userBannedPromise;
+        });
+    });
+});
+
+
 describe("Kicking on IRC join", () => {
     const {env, config, test} = envBundle();
 
diff --git a/src/bridge/IrcBridge.ts b/src/bridge/IrcBridge.ts
index 0aa94780f..8cd71bd46 100644
--- a/src/bridge/IrcBridge.ts
+++ b/src/bridge/IrcBridge.ts
@@ -1254,18 +1254,20 @@ export class IrcBridge {
             else if (event.content.membership === "join") {
                 await this.matrixHandler.onJoin(request, memberEvent as unknown as OnMemberEventData, target);
             }
-            else if (["ban", "leave"].includes(event.content.membership as string)) {
-                // Given a "self-kick" is a leave, and you can't ban yourself,
-                // if the 2 IDs are different then we know it is either a kick
-                // or a ban (or a rescinded invite)
-                const isKickOrBan = target.getId() !== sender.getId();
-                if (isKickOrBan) {
+            else if (event.content.membership === "leave") {
+                // Given a "self-kick" is a leave, if the 2 IDs are different then
+                // we know it is a kick (or a rescinded invite)
+                const isKick = target.getId() !== sender.getId();
+                if (isKick) {
                     await this.matrixHandler.onKick(request, memberEvent as unknown as MatrixEventKick, sender, target);
                 }
                 else {
                     await this.matrixHandler.onLeave(request, memberEvent, target);
                 }
             }
+            else if (event.content.membership === "ban") {
+                await this.matrixHandler.onBan(request, memberEvent as unknown as MatrixEventKick, sender, target);
+            }
         }
         else if (event.type === "m.room.power_levels" && event.state_key === "") {
             this.ircHandler.roomAccessSyncer.onMatrixPowerlevelEvent(event);
diff --git a/src/bridge/MatrixHandler.ts b/src/bridge/MatrixHandler.ts
index 4e4616732..22d5535e0 100644
--- a/src/bridge/MatrixHandler.ts
+++ b/src/bridge/MatrixHandler.ts
@@ -652,7 +652,7 @@ export class MatrixHandler {
 
     private async _onKick(req: BridgeRequest, event: MatrixEventKick, kicker: MatrixUser, kickee: MatrixUser) {
         req.log.info(
-            "onKick %s is kicking/banning %s from %s (reason: %s)",
+            "onKick %s is kicking %s from %s (reason: %s)",
             kicker.getId(), kickee.getId(), event.room_id, event.content.reason || "none"
         );
         this._onMemberEvent(req, event);
@@ -741,7 +741,81 @@ export class MatrixHandler {
                 // If we aren't joined this will no-op.
                 await client.leaveChannel(
                     ircRoom.channel,
-                    `Kicked by ${kicker.getId()} ` +
+                    `Kicked by ${kicker.getId()}` +
+                    (event.content.reason ? ` : ${event.content.reason}` : "")
+                );
+            })));
+        }
+    }
+
+    private async _onBan(req: BridgeRequest, event: MatrixEventKick, sender: MatrixUser, banned: MatrixUser) {
+        req.log.info(
+            "onBan %s is banning %s from %s (reason: %s)",
+            sender.getId(), banned.getId(), event.room_id, event.content.reason || "none"
+        );
+        this._onMemberEvent(req, event);
+
+        const ircRooms = await this.ircBridge.getStore().getIrcChannelsForRoomId(event.room_id);
+        // do we have an active connection for the banned? This tells us if they are real
+        // or virtual.
+        const bannedClients = this.ircBridge.getBridgedClientsForUserId(banned.getId());
+
+        if (bannedClients.length === 0) {
+            // Matrix on IRC banning, work out which IRC user to ban.
+            let server = null;
+            for (let i = 0; i < ircRooms.length; i++) {
+                if (ircRooms[i].server.claimsUserId(banned.getId())) {
+                    server = ircRooms[i].server;
+                    break;
+                }
+            }
+            if (!server) {
+                return; // kicking a bogus user
+            }
+            const bannedNick = server.getNickFromUserId(banned.getId());
+            if (!bannedNick) {
+                return; // bogus virtual user ID
+            }
+            // work out which client will do the kicking
+            const senderClient = this.ircBridge.getIrcUserFromCache(server, sender.getId());
+            if (!senderClient) {
+                // well this is awkward.. whine about it and bail.
+                req.log.warn(
+                    "%s has no client instance to send kick from. Cannot kick.",
+                    sender.getId()
+                );
+                return;
+            }
+            // we may be bridging this matrix room into many different IRC channels, and we want
+            // to kick this user from all of them.
+            for (let i = 0; i < ircRooms.length; i++) {
+                if (ircRooms[i].server.domain !== server.domain) {
+                    return;
+                }
+                senderClient.ban(bannedNick, ircRooms[i].channel);
+                senderClient.kick(
+                    bannedNick, ircRooms[i].channel,
+                    `Banned by ${sender.getId()}` +
+                    (event.content.reason ? ` : ${event.content.reason}` : "")
+                );
+            }
+        }
+        else {
+            // Matrix on Matrix banning: part the channel.
+            const bannedServerLookup: {[serverDomain: string]: BridgedClient} = {};
+            bannedClients.forEach((ircClient) => {
+                bannedServerLookup[ircClient.server.domain] = ircClient;
+            });
+            await Promise.all(ircRooms.map((async (ircRoom) => {
+                // Make the connected IRC client leave the channel.
+                const client = bannedServerLookup[ircRoom.server.domain];
+                if (!client) {
+                    return; // not connected to this server
+                }
+                // If we aren't joined this will no-op.
+                await client.leaveChannel(
+                    ircRoom.channel,
+                    `Banned by ${sender.getId()}` +
                     (event.content.reason ? ` : ${event.content.reason}` : "")
                 );
             })));
@@ -1464,6 +1538,10 @@ export class MatrixHandler {
         return reqHandler(req, this._onKick(req, event, kicker, kickee));
     }
 
+    public onBan(req: BridgeRequest, event: MatrixEventKick, sender: MatrixUser, banned: MatrixUser) {
+        return reqHandler(req, this._onBan(req, event, sender, banned));
+    }
+
     public onMessage(req: BridgeRequest, event: MatrixMessageEvent) {
         return reqHandler(req, this._onMessage(req, event));
     }
diff --git a/src/irc/BridgedClient.ts b/src/irc/BridgedClient.ts
index 932bceb47..238746adf 100644
--- a/src/irc/BridgedClient.ts
+++ b/src/irc/BridgedClient.ts
@@ -510,6 +510,26 @@ export class BridgedClient extends EventEmitter {
         await c.send("KICK", channel, nick, reason);
     }
 
+    public async ban(nick: string, channel: string): Promise<void> {
+        if (this.state.status !== BridgedClientStatus.CONNECTED) {
+            return; // we were never connected to the network.
+        }
+        if (!this.state.client.chans.has(channel)) {
+            // we were never joined to it. We need to be joined to it to kick people.
+            return;
+        }
+        if (!channel.startsWith("#")) {
+            return; // PM room
+        }
+
+        const c = this.state.client;
+
+        this.log.debug("Banning %s from channel %s", nick, channel);
+
+        // best effort ban
+        await c.send("MODE", channel, "+b", nick + "!*@*");
+    }
+
     public sendAction(room: IrcRoom, action: IrcAction) {
         this.keepAlive();
         let expiryTs = 0;