diff --git a/src/components/views/context_menus/MessageContextMenu.js b/src/components/views/context_menus/MessageContextMenu.js
index d760c8defa..bc4514f8a6 100644
--- a/src/components/views/context_menus/MessageContextMenu.js
+++ b/src/components/views/context_menus/MessageContextMenu.js
@@ -31,6 +31,7 @@ import SettingsStore from '../../../settings/SettingsStore';
 import { isUrlPermitted } from '../../../HtmlUtils';
 import { isContentActionable } from '../../../utils/EventUtils';
 import {MenuItem} from "../../structures/ContextMenu";
+import {EventType} from "matrix-js-sdk/src/@types/event";
 
 function canCancel(eventStatus) {
     return eventStatus === EventStatus.QUEUED || eventStatus === EventStatus.NOT_SENT;
@@ -72,7 +73,10 @@ export default class MessageContextMenu extends React.Component {
         const cli = MatrixClientPeg.get();
         const room = cli.getRoom(this.props.mxEvent.getRoomId());
 
-        const canRedact = room.currentState.maySendRedactionForEvent(this.props.mxEvent, cli.credentials.userId);
+        // We explicitly decline to show the redact option on ACL events as it has a potential
+        // to obliterate the room - https://github.com/matrix-org/synapse/issues/4042
+        const canRedact = room.currentState.maySendRedactionForEvent(this.props.mxEvent, cli.credentials.userId)
+            && this.props.mxEvent.getType() !== EventType.RoomServerAcl;
         let canPin = room.currentState.mayClientSendStateEvent('m.room.pinned_events', cli);
 
         // HACK: Intentionally say we can't pin if the user doesn't want to use the functionality
diff --git a/src/components/views/right_panel/UserInfo.tsx b/src/components/views/right_panel/UserInfo.tsx
index dd291b1fa1..f8be6327bf 100644
--- a/src/components/views/right_panel/UserInfo.tsx
+++ b/src/components/views/right_panel/UserInfo.tsx
@@ -60,6 +60,7 @@ import ErrorDialog from "../dialogs/ErrorDialog";
 import QuestionDialog from "../dialogs/QuestionDialog";
 import ConfirmUserActionDialog from "../dialogs/ConfirmUserActionDialog";
 import InfoDialog from "../dialogs/InfoDialog";
+import { EventType } from "matrix-js-sdk/src/@types/event";
 
 interface IDevice {
     deviceId: string;
@@ -586,7 +587,10 @@ const RedactMessagesButton: React.FC<IBaseProps> = ({member}) => {
         while (timeline) {
             eventsToRedact = timeline.getEvents().reduce((events, event) => {
                 if (event.getSender() === userId && !event.isRedacted() && !event.isRedaction() &&
-                    event.getType() !== "m.room.create"
+                    event.getType() !== EventType.RoomCreate &&
+                    // Don't redact ACLs because that'll obliterate the room
+                    // See https://github.com/matrix-org/synapse/issues/4042 for details.
+                    event.getType() !== EventType.RoomServerAcl
                 ) {
                     return events.concat(event);
                 } else {