diff --git a/src/App.js b/src/App.js
index b3de033b0..dcb7ba8f9 100644
--- a/src/App.js
+++ b/src/App.js
@@ -88,7 +88,8 @@ export default class App extends PureComponent {
           });
           break;
         case 'GitLab':
-          const gitlabOAuth = createGitlabOAuth();
+          let project = getPersistedField('gitLabURL');
+          const gitlabOAuth = createGitlabOAuth(project);
           if (gitlabOAuth.isAuthorized()) {
             client = createGitLabSyncBackendClient(gitlabOAuth);
             initialState.syncBackend = Map({
diff --git a/src/components/SyncServiceSignIn/index.js b/src/components/SyncServiceSignIn/index.js
index 487466a94..ee80d6a5c 100644
--- a/src/components/SyncServiceSignIn/index.js
+++ b/src/components/SyncServiceSignIn/index.js
@@ -10,7 +10,6 @@ import GitLabLogo from './gitlab.svg';
 import { persistField } from '../../util/settings_persister';
 import {
   createGitlabOAuth,
-  gitLabProjectIdFromURL,
 } from '../../sync_backend_clients/gitlab_sync_backend_client';
 
 import { DropboxAuth } from 'dropbox';
@@ -113,15 +112,10 @@ function GitLab() {
   const defaultProject = 'https://gitlab.com/your/project';
   const [project, setProject] = useState(defaultProject);
   const handleSubmit = (evt) => {
-    const projectId = gitLabProjectIdFromURL(project);
-    if (projectId) {
-      persistField('authenticatedSyncService', 'GitLab');
-      persistField('gitLabProject', projectId);
-      createGitlabOAuth().fetchAuthorizationCode();
-    } else {
-      evt.preventDefault();
-      alert('Project does not appear to be a valid gitlab.com URL');
-    }
+    persistField('authenticatedSyncService', 'GitLab');
+    persistField('gitLabURL', project);
+    // TODO handle incorrect URLs, possibly with try ... catch ...
+    createGitlabOAuth(project).fetchAuthorizationCode();
   };
 
   return (
diff --git a/src/sync_backend_clients/gitlab_sync_backend_client.js b/src/sync_backend_clients/gitlab_sync_backend_client.js
index 92fefc7ee..b50a13f3b 100644
--- a/src/sync_backend_clients/gitlab_sync_backend_client.js
+++ b/src/sync_backend_clients/gitlab_sync_backend_client.js
@@ -5,15 +5,16 @@ import { getPersistedField } from '../util/settings_persister';
 
 import { fromJS, Map } from 'immutable';
 
-export const createGitlabOAuth = () => {
+export const createGitlabOAuth = (url = 'https://gitlab.com') => {
   // Use promises as mutex to prevent concurrent token refresh attempts, which causes problems.
   // More info: https://github.com/BitySA/oauth2-auth-code-pkce/issues/29
   // TODO: remove this workaround if/when oauth2-auth-code-pkce fixes the issue.
   let expiryPromise;
   let invalidGrantPromise;
+  url = new URL(url)
   return new OAuth2AuthCodePKCE({
-    authorizationUrl: 'https://gitlab.com/oauth/authorize',
-    tokenUrl: 'https://gitlab.com/oauth/token',
+    authorizationUrl: url.origin + '/oauth/authorize',
+    tokenUrl: url.origin + '/oauth/token',
     clientId: process.env.REACT_APP_GITLAB_CLIENT_ID,
     redirectUrl: window.location.origin,
     scopes: ['api'],
@@ -64,7 +65,7 @@ export const gitLabProjectIdFromURL = (projectURL) => {
     // to a project. Reminder: a project path is not necessarily
     // /user/project because it may be under one or more groups such
     // as /user/group/subgroup/project.
-    if (url.hostname === 'gitlab.com' && path.split('/').length > 1) {
+    if (path.split('/').length > 1) {
       return encodeURIComponent(path);
     } else {
       return undefined;
@@ -130,7 +131,7 @@ export const treeToDirectoryListing = (tree) => {
   );
 };
 
-const API_URL = 'https://gitlab.com/api/v4';
+const API_PATH = '/api/v4/'
 
 /**
  * GitLab sync backend, implemented using their REST API.
@@ -141,7 +142,14 @@ const API_URL = 'https://gitlab.com/api/v4';
 export default (oauthClient) => {
   const decoratedFetch = oauthClient.decorateFetchHTTPClient(fetch);
 
-  const getProjectApi = () => `${API_URL}/projects/${getPersistedField('gitLabProject')}`;
+  const getApi = () => {
+    let url = new URL(getPersistedField('gitLabURL'))
+    return url.origin + API_PATH
+  }
+
+  const getProject = () => gitLabProjectIdFromURL(getPersistedField('gitLabURL'))
+
+  const getProjectApi = () => getApi() + 'projects/' + getProject()
 
   const isSignedIn = async () => {
     if (!oauthClient.isAuthorized()) {
@@ -174,7 +182,7 @@ export default (oauthClient) => {
     // commit.
     const [userResponse, membersResponse] = await Promise.all([
       // https://docs.gitlab.com/ee/api/users.html#list-current-user-for-normal-users
-      decoratedFetch(`${API_URL}/user`),
+      decoratedFetch(getApi() + 'user'),
       // https://docs.gitlab.com/ee/api/members.html#list-all-members-of-a-group-or-project
       decoratedFetch(`${getProjectApi()}/members`),
     ]);
diff --git a/src/sync_backend_clients/gitlab_sync_backend_client.test.js b/src/sync_backend_clients/gitlab_sync_backend_client.test.js
index 24d285916..10192fd13 100644
--- a/src/sync_backend_clients/gitlab_sync_backend_client.test.js
+++ b/src/sync_backend_clients/gitlab_sync_backend_client.test.js
@@ -17,6 +17,21 @@ test('Parses GitLab project from URL', () => {
   });
 });
 
+test('Parses GitLab project from URL of a self-managed GitLab instance', () => {
+  [
+    ['https://mygitlab.com/user/foo', 'user%2Ffoo'],
+    ['https://mygitlab.com/group/subgroup/project', 'group%2Fsubgroup%2Fproject'],
+    ['mygitlab.com/foo/bar', 'foo%2Fbar'],
+    ['mygitlab.com/user-but-no-project', undefined],
+    ['https://www.mygitlab.com/user/foo', 'user%2Ffoo'],
+    ['https://www.mygitlab.com/group/subgroup/project', 'group%2Fsubgroup%2Fproject'],
+    ['www.mygitlab.com/foo/bar', 'foo%2Fbar'],
+    ['www.mygitlab.com/user-but-no-project', undefined],
+  ].forEach(([input, expected]) => {
+    expect(gitLabProjectIdFromURL(input)).toEqual(expected);
+  });
+});
+
 test('Parses Link pagination header', () => {
   [
     [null, {}],