diff --git a/src/CourseAuthoringPage.jsx b/src/CourseAuthoringPage.jsx
index b11dcc7948..3e6b50f2e3 100644
--- a/src/CourseAuthoringPage.jsx
+++ b/src/CourseAuthoringPage.jsx
@@ -9,6 +9,7 @@ import { StudioFooter } from '@edx/frontend-component-footer';
 import Header from './header';
 import { fetchCourseDetail } from './data/thunks';
 import { useModel } from './generic/model-store';
+import NotFoundAlert from './generic/NotFoundAlert';
 import PermissionDeniedAlert from './generic/PermissionDeniedAlert';
 import { getCourseAppsApiStatus } from './pages-and-resources/data/selectors';
 import { RequestStatus } from './data/constants';
@@ -50,10 +51,16 @@ const CourseAuthoringPage = ({ courseId, children }) => {
   const courseOrg = courseDetail ? courseDetail.org : null;
   const courseTitle = courseDetail ? courseDetail.name : courseId;
   const courseAppsApiStatus = useSelector(getCourseAppsApiStatus);
-  const inProgress = useSelector(state => state.courseDetail.status) === RequestStatus.IN_PROGRESS;
+  const courseDetailStatus = useSelector(state => state.courseDetail.status);
+  const inProgress = courseDetailStatus === RequestStatus.IN_PROGRESS;
   const { pathname } = useLocation();
   const showHeader = !pathname.includes('/editor');
 
+  if (courseDetailStatus === RequestStatus.NOT_FOUND) {
+    return (
+      <NotFoundAlert />
+    );
+  }
   if (courseAppsApiStatus === RequestStatus.DENIED) {
     return (
       <PermissionDeniedAlert />
diff --git a/src/CourseAuthoringPage.test.jsx b/src/CourseAuthoringPage.test.jsx
index 3e982c5929..c7eeeb9be8 100644
--- a/src/CourseAuthoringPage.test.jsx
+++ b/src/CourseAuthoringPage.test.jsx
@@ -12,6 +12,7 @@ import CourseAuthoringPage from './CourseAuthoringPage';
 import PagesAndResources from './pages-and-resources/PagesAndResources';
 import { executeThunk } from './utils';
 import { fetchCourseApps } from './pages-and-resources/data/thunks';
+import { fetchCourseDetail } from './data/thunks';
 
 const courseId = 'course-v1:edX+TestX+Test_Course';
 let mockPathname = '/evilguy/';
@@ -24,6 +25,19 @@ jest.mock('react-router-dom', () => ({
 let axiosMock;
 let store;
 
+beforeEach(() => {
+  initializeMockApp({
+    authenticatedUser: {
+      userId: 3,
+      username: 'abc123',
+      administrator: true,
+      roles: [],
+    },
+  });
+  store = initializeStore();
+  axiosMock = new MockAdapter(getAuthenticatedHttpClient());
+});
+
 describe('Editor Pages Load no header', () => {
   const mockStoreSuccess = async () => {
     const apiBaseUrl = getConfig().STUDIO_BASE_URL;
@@ -33,18 +47,6 @@ describe('Editor Pages Load no header', () => {
     });
     await executeThunk(fetchCourseApps(courseId), store.dispatch);
   };
-  beforeEach(() => {
-    initializeMockApp({
-      authenticatedUser: {
-        userId: 3,
-        username: 'abc123',
-        administrator: true,
-        roles: [],
-      },
-    });
-    store = initializeStore();
-    axiosMock = new MockAdapter(getAuthenticatedHttpClient());
-  });
   test('renders no loading wheel on editor pages', async () => {
     mockPathname = '/editor/';
     await mockStoreSuccess();
@@ -76,3 +78,56 @@ describe('Editor Pages Load no header', () => {
     expect(wrapper.queryByRole('status')).toBeInTheDocument();
   });
 });
+
+describe('Course authoring page', () => {
+  const lmsApiBaseUrl = getConfig().LMS_BASE_URL;
+  const courseDetailApiUrl = `${lmsApiBaseUrl}/api/courses/v1/courses`;
+  const mockStoreNotFound = async () => {
+    axiosMock.onGet(
+      `${courseDetailApiUrl}/${courseId}?username=abc123`,
+    ).reply(404, {
+      response: { status: 404 },
+    });
+    await executeThunk(fetchCourseDetail(courseId), store.dispatch);
+  };
+  const mockStoreError = async () => {
+    axiosMock.onGet(
+      `${courseDetailApiUrl}/${courseId}?username=abc123`,
+    ).reply(500, {
+      response: { status: 500 },
+    });
+    await executeThunk(fetchCourseDetail(courseId), store.dispatch);
+  };
+  test('renders not found page on non-existent course key', async () => {
+    await mockStoreNotFound();
+    const wrapper = render(
+      <AppProvider store={store}>
+        <IntlProvider locale="en">
+          <CourseAuthoringPage courseId={courseId} />
+        </IntlProvider>
+      </AppProvider>
+      ,
+    );
+    expect(await wrapper.findByTestId('notFoundAlert')).toBeInTheDocument();
+  });
+  test('does not render not found page on other kinds of error', async () => {
+    await mockStoreError();
+    // Currently, loading errors are not handled, so we wait for the child
+    // content to be rendered -which happens when request status is no longer
+    // IN_PROGRESS but also not NOT_FOUND or DENIED- then check that the not
+    // found alert is not present.
+    const contentTestId = 'courseAuthoringPageContent';
+    const wrapper = render(
+      <AppProvider store={store}>
+        <IntlProvider locale="en">
+          <CourseAuthoringPage courseId={courseId}>
+            <div data-testid={contentTestId} />
+          </CourseAuthoringPage>
+        </IntlProvider>
+      </AppProvider>
+      ,
+    );
+    expect(await wrapper.findByTestId(contentTestId)).toBeInTheDocument();
+    expect(wrapper.queryByTestId('notFoundAlert')).not.toBeInTheDocument();
+  });
+});
diff --git a/src/data/constants.js b/src/data/constants.js
index 5191ea1dfa..bd01f09dda 100644
--- a/src/data/constants.js
+++ b/src/data/constants.js
@@ -13,6 +13,7 @@ export const RequestStatus = {
   PENDING: 'pending',
   CLEAR: 'clear',
   PARTIAL: 'partial',
+  NOT_FOUND: 'not-found',
 };
 
 /**
diff --git a/src/data/thunks.js b/src/data/thunks.js
index 9a52d4d89d..9c797dc6a5 100644
--- a/src/data/thunks.js
+++ b/src/data/thunks.js
@@ -21,7 +21,11 @@ export function fetchCourseDetail(courseId) {
         canChangeProviders: getAuthenticatedUser().administrator || new Date(courseDetail.start) > new Date(),
       }));
     } catch (error) {
-      dispatch(updateStatus({ courseId, status: RequestStatus.FAILED }));
+      if (error.response && error.response.status === 404) {
+        dispatch(updateStatus({ courseId, status: RequestStatus.NOT_FOUND }));
+      } else {
+        dispatch(updateStatus({ courseId, status: RequestStatus.FAILED }));
+      }
     }
   };
 }
diff --git a/src/generic/NotFoundAlert.jsx b/src/generic/NotFoundAlert.jsx
new file mode 100644
index 0000000000..8ff9cf4fff
--- /dev/null
+++ b/src/generic/NotFoundAlert.jsx
@@ -0,0 +1,14 @@
+import React from 'react';
+import { FormattedMessage } from '@edx/frontend-platform/i18n';
+import { Alert } from '@edx/paragon';
+
+const NotFoundAlert = () => (
+  <Alert variant="danger" data-testid="notFoundAlert">
+    <FormattedMessage
+      id="authoring.alert.error.notfound"
+      defaultMessage="Not found."
+    />
+  </Alert>
+);
+
+export default NotFoundAlert;