diff --git a/src/InvalidUrlView.js b/src/InvalidUrlView.js
new file mode 100644
index 0000000..e6a58e7
--- /dev/null
+++ b/src/InvalidUrlView.js
@@ -0,0 +1,29 @@
+/*
+Copyright 2021 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 {TemplateView} from "./utils/TemplateView.js";
+
+export class InvalidUrlView extends TemplateView {
+    render(t) {
+        return t.div({ className: "DisclaimerView card" }, [
+            t.h1("Invalid URL"),
+            t.p([
+                'The link you have entered is not valid. If you like, you can ',
+                t.a({ href: "#/" }, 'return to the home page.')
+            ]),
+        ]);
+    }
+}
diff --git a/src/RootView.js b/src/RootView.js
index 5669f36..218ad57 100644
--- a/src/RootView.js
+++ b/src/RootView.js
@@ -19,10 +19,12 @@ import {OpenLinkView} from "./open/OpenLinkView.js";
 import {CreateLinkView} from "./create/CreateLinkView.js";
 import {LoadServerPolicyView} from "./policy/LoadServerPolicyView.js";
 import {DisclaimerView} from "./disclaimer/DisclaimerView.js";
+import {InvalidUrlView} from "./InvalidUrlView.js";
 
 export class RootView extends TemplateView {
     render(t, vm) {
         return t.div({className: "RootView"}, [
+            t.mapView(vm => vm.invalidUrl, invalid => invalid ? new InvalidUrlView() : null),
             t.mapView(vm => vm.showDisclaimer, disclaimer => disclaimer ? new DisclaimerView() : null),
             t.mapView(vm => vm.openLinkViewModel, vm => vm ? new OpenLinkView(vm) : null),
             t.mapView(vm => vm.createLinkViewModel, vm => vm ? new CreateLinkView(vm) : null),
diff --git a/src/RootViewModel.js b/src/RootViewModel.js
index 2cc1070..b9cde3f 100644
--- a/src/RootViewModel.js
+++ b/src/RootViewModel.js
@@ -30,6 +30,7 @@ export class RootViewModel extends ViewModel {
         this.createLinkViewModel = null;
         this.loadServerPolicyViewModel = null;
         this.showDisclaimer = false;
+        this.invalidUrl = false;
         this.preferences.on("canClear", () => {
             this.emitChange();
         });
@@ -58,6 +59,7 @@ export class RootViewModel extends ViewModel {
         // clear them to avoid having to manually reset (n-1)/n view models in every case.
         // That just doesn't scale well when we add new views.
         const oldLink = this.link;
+        this.invalidUrl = false;
         this.showDisclaimer = false;
         this.loadServerPolicyViewModel = null;
         this.createLinkViewModel = null;
@@ -75,6 +77,9 @@ export class RootViewModel extends ViewModel {
             this.createLinkViewModel = new CreateLinkViewModel(this.childOptions());
         } else if (newLink = Link.parse(hash)) {
             this._updateChildVMs(newLink, oldLink);
+        } else {
+            this._updateChildVMs(null, oldLink);
+            this.invalidUrl = true;
         }
         this.emitChange();
     }