diff --git a/CHANGELOG.md b/CHANGELOG.md
index aee3240..3835328 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+### Added
+
+- Admins can clear the whole chat history (*Admin → Chat*, or `DELETE /rigshare/api/chat`). Everyone's chat empties at once, followed by a notice saying who cleared it
+
 ### Fixed
 
 - Entering the App view closed an open RigShare or Files panel (going back to the graph kept it open). It now stays open both ways
diff --git a/docs/api.md b/docs/api.md
index 5f6b9d9..0f4e368 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -47,6 +47,7 @@ The panel uses these; they take the same session cookie or API key.
 | `GET /rigshare/api/me` | The current account |
 | `GET/POST /rigshare/api/me/keys`, `DELETE /rigshare/api/me/keys/{id}` | Your API keys |
 | `GET /rigshare/api/chat?before=<seq>&limit=50` | Older chat messages, oldest first, and whether more exist |
+| `DELETE /rigshare/api/chat` | Clear the whole chat history (admin) |
 | `GET /rigshare/api/rooms` | Live workflows |
 | `GET /rigshare/api/room?key=…` | One room, with its workflow JSON |
 | `GET /rigshare/api/snapshots?room=…` | History of a room |
diff --git a/docs/settings.md b/docs/settings.md
index 43c3c44..8ea42b3 100644
--- a/docs/settings.md
+++ b/docs/settings.md
@@ -34,7 +34,7 @@ Admins change these under **Admin → Server settings**. They are stored in `rig
 | `room_expiry_days` | `14` | Forget the live state of workflows nobody opened for this long |
 | `snapshot_interval_sec` | `300` | Automatic snapshot interval while editing; `0` turns it off |
 | `snapshot_keep` | `30` | Automatic snapshots kept per workflow, and as many on-save ones; named ones are always kept |
-| `chat_keep` | `0` | Chat messages kept: `0` keeps the whole history, a number trims it to the latest ones at startup |
+| `chat_keep` | `0` | Chat messages kept: `0` keeps the whole history, a number trims it to the latest ones at startup. Admins can also clear it under *Admin → Chat* |
 
 ## Environment variables
 
diff --git a/rigshare_core/chatlog.py b/rigshare_core/chatlog.py
index 2bd111f..8a6a709 100644
--- a/rigshare_core/chatlog.py
+++ b/rigshare_core/chatlog.py
@@ -57,6 +57,13 @@ class ChatLog:
         os.replace(tmp, self.path)
         self._index()
 
+    def clear(self):
+        """Delete the whole history; numbering starts again at 0."""
+        with self._lock:
+            with open(self.path, "w", encoding="utf-8"):
+                pass
+            self.offsets = []
+
     def __len__(self):
         return len(self.offsets)
 
diff --git a/rigshare_core/hub.py b/rigshare_core/hub.py
index 0059775..6470e96 100644
--- a/rigshare_core/hub.py
+++ b/rigshare_core/hub.py
@@ -381,6 +381,12 @@ class Hub:
     async def broadcast_server(self):
         await self.broadcast({"type": "server", "server": self.server_info()})
 
+    async def clear_chat(self, by):
+        """An admin wiped the chat: everyone's history empties, then a notice says who."""
+        self.chat.clear()
+        await self.broadcast({"type": "chat_cleared"})
+        await self.system_chat(f"{by} cleared the chat history")
+
     async def system_chat(self, text):
         msg = {"id": secrets.token_hex(6), "system": True, "text": text, "ts": int(time.time() * 1000)}
         msg = self.chat.append(msg)
diff --git a/rigshare_core/routes.py b/rigshare_core/routes.py
index 23eb79d..f1cc921 100644
--- a/rigshare_core/routes.py
+++ b/rigshare_core/routes.py
@@ -356,6 +356,13 @@ def setup(server, store, hub):
         messages, more = hub.chat.page(before, limit)
         return web.json_response({"messages": messages, "more": more})
 
+    @routes.delete("/rigshare/api/chat")
+    async def clear_chat(request):
+        admin = require_admin(request)
+        await hub.clear_chat(admin.get("display_name") or admin["username"])
+        log.info(f"[RigShare] {admin['username']} cleared the chat history")
+        return web.json_response({"ok": True})
+
     @routes.get("/rigshare/api/rooms")
     async def list_rooms(request):
         return web.json_response([r for r in hub.room_list() if room_access(request, hub.rooms[r["key"]])])
diff --git a/tests/python/test_server.py b/tests/python/test_server.py
index 5f4c2ac..0259a52 100644
--- a/tests/python/test_server.py
+++ b/tests/python/test_server.py
@@ -440,3 +440,26 @@ def test_every_save_keeps_a_snapshot(run):
             await h.post(rig.url(f"/api/userdata/{enc(path)}"), data=b'{"nodes": []}', headers=viewer)
             assert len(rig.store.list_snapshots("file:" + path)) == 2
     run(scenario())
+
+
+def test_admin_clears_chat_history(run):
+    async def scenario():
+        async with rig_server() as rig:
+            admin = await rig.setup_admin()
+            alice = await rig.add_user("alice", edit=True)
+            sock = await rig.ws("alice")
+            for i in range(5):
+                await sock.send({"type": "chat", "text": f"hi {i}"})
+            await asyncio.sleep(0.2)
+            await sock.drain()
+            assert (await rig.http.delete(rig.url("/rigshare/api/chat"), headers=alice)).status == 403, "admins only"
+            assert (await rig.http.delete(rig.url("/rigshare/api/chat"), headers=admin)).status == 200
+            msgs = await sock.drain()
+            kinds = [m["type"] for m in msgs]
+            assert "chat_cleared" in kinds and kinds.index("chat_cleared") < kinds.index("chat")
+            notice = next(m for m in msgs if m["type"] == "chat")["message"]
+            assert notice["system"] and "cleared the chat history" in notice["text"] and notice["seq"] == 0
+            history = await (await rig.http.get(rig.url("/rigshare/api/chat"), headers=alice)).json()
+            assert [m["text"] for m in history["messages"]] == [notice["text"]] and not history["more"]
+            await sock.close()
+    run(scenario())
diff --git a/web/rigshare/client.js b/web/rigshare/client.js
index f5ddb8a..6f1b753 100644
--- a/web/rigshare/client.js
+++ b/web/rigshare/client.js
@@ -146,6 +146,11 @@ export class RigClient extends EventTarget {
                 this.stats = msg.stats;
                 this.emit("stats", msg.stats);
                 break;
+            case "chat_cleared":
+                this.chat = [];
+                this.chatMore = false;
+                this.emit("chat-history", this.chat);
+                break;
             case "chat":
                 this.chat.push(msg.message);
                 this.emit("chat", msg.message);
diff --git a/web/rigshare/panel.js b/web/rigshare/panel.js
index 70944bc..fc456e3 100644
--- a/web/rigshare/panel.js
+++ b/web/rigshare/panel.js
@@ -687,6 +687,14 @@ export class RigSharePanel {
         return [
             this.section("pi-users", "Accounts", this.adminAccounts, this.createAccountForm()),
             this.section("pi-cog", "Server settings", this.adminSettings),
+            this.section("pi-comments", "Chat",
+                h("p", { class: "rs-muted rs-small" }, "The whole chat history is kept. Clearing it deletes every message for everyone; it cannot be undone."),
+                h("div", { class: "rs-actions" }, h("button", {
+                    class: "rs-btn rs-danger", onclick: async () => {
+                        if (!(await this.confirm("Clear chat history", "Delete every chat message for everyone? This cannot be undone."))) return;
+                        await this.run(() => this.client.request("DELETE", "/rigshare/api/chat"), "Chat history cleared");
+                    },
+                }, h("i", { class: "pi pi-trash" }), "Clear chat history"))),
         ];
     }