diff --git a/.env.development b/.env.development
index f328914..d5ee466 100644
--- a/.env.development
+++ b/.env.development
@@ -1,8 +1,12 @@
 # This file is committed to git and should not contain any secrets.
-# 
+#
 # Vite recommends using .env.local or .env.[mode].local if you need to manage secrets
 # SEE: https://vite.dev/guide/env-and-mode.html#env-files for more information.
 
 
 # Default NODE_ENV with vite build --mode=test is production
 NODE_ENV=development
+
+# OpenStreetMap OAuth
+VITE_OSM_CLIENT_ID=jIn8l5mT8FZOGYiIYXG1Yvj_2FZKB9TJ1edZwOJPsRU
+VITE_OSM_OAUTH_URL=https://www.openstreetmap.org
diff --git a/app/components/user-menu.gjs b/app/components/user-menu.gjs
index db689ad..7abacd9 100644
--- a/app/components/user-menu.gjs
+++ b/app/components/user-menu.gjs
@@ -1,9 +1,13 @@
 import Component from '@glimmer/component';
 import { action } from '@ember/object';
+import { service } from '@ember/service';
 import Icon from '#components/icon';
 import { on } from '@ember/modifier';
 
 export default class UserMenuComponent extends Component {
+  @service storage;
+  @service osmAuth;
+
   @action
   connectRS() {
     this.args.onClose();
@@ -15,6 +19,17 @@ export default class UserMenuComponent extends Component {
     this.args.storage.disconnect();
   }
 
+  @action
+  connectOsm() {
+    this.args.onClose();
+    this.osmAuth.login();
+  }
+
+  @action
+  disconnectOsm() {
+    this.osmAuth.logout();
+  }
+
   <template>
     <div class="user-menu-popover">
       <ul class="account-list">
@@ -40,22 +55,39 @@ export default class UserMenuComponent extends Component {
           </div>
           <div class="account-status">
             {{#if @storage.connected}}
-              <strong>{{@storage.userAddress}}</strong>
+              {{@storage.userAddress}}
             {{else}}
               Not connected
             {{/if}}
           </div>
         </li>
 
-        <li class="account-item disabled">
+        <li class="account-item">
           <div class="account-header">
             <div class="account-info">
               <Icon @name="map" @size={{18}} />
               <span>OpenStreetMap</span>
             </div>
+            {{#if this.osmAuth.isConnected}}
+              <button
+                class="btn-text text-danger"
+                type="button"
+                {{on "click" this.disconnectOsm}}
+              >Disconnect</button>
+            {{else}}
+              <button
+                class="btn-text text-primary"
+                type="button"
+                {{on "click" this.connectOsm}}
+              >Connect</button>
+            {{/if}}
           </div>
           <div class="account-status">
-            Coming soon
+            {{#if this.osmAuth.isConnected}}
+              {{this.osmAuth.userDisplayName}}
+            {{else}}
+              Not connected
+            {{/if}}
           </div>
         </li>
 
diff --git a/app/router.js b/app/router.js
index 170d769..24dc1a4 100644
--- a/app/router.js
+++ b/app/router.js
@@ -10,4 +10,7 @@ Router.map(function () {
   this.route('place', { path: '/place/:place_id' });
   this.route('place.new', { path: '/place/new' });
   this.route('search');
+  this.route('oauth', function () {
+    this.route('osm-callback', { path: '/osm/callback' });
+  });
 });
diff --git a/app/routes/oauth/osm-callback.js b/app/routes/oauth/osm-callback.js
new file mode 100644
index 0000000..2a5b665
--- /dev/null
+++ b/app/routes/oauth/osm-callback.js
@@ -0,0 +1,17 @@
+import Route from '@ember/routing/route';
+import { service } from '@ember/service';
+
+export default class OauthOsmCallbackRoute extends Route {
+  @service osmAuth;
+  @service router;
+
+  async model() {
+    try {
+      await this.osmAuth.handleCallback();
+    } catch (e) {
+      console.error('Failed to handle OSM OAuth callback', e);
+    } finally {
+      this.router.transitionTo('index');
+    }
+  }
+}
diff --git a/app/services/osm-auth.js b/app/services/osm-auth.js
new file mode 100644
index 0000000..23dddc9
--- /dev/null
+++ b/app/services/osm-auth.js
@@ -0,0 +1,103 @@
+import Service from '@ember/service';
+import { tracked } from '@glimmer/tracking';
+import { OAuth2AuthCodePkceClient } from 'oauth2-pkce';
+
+class MarcoOsmAuthStorage {
+  saveState(serializedState) {
+    localStorage.setItem('marco:osm_auth_state', serializedState);
+  }
+  loadState() {
+    return localStorage.getItem('marco:osm_auth_state');
+  }
+}
+
+export default class OsmAuthService extends Service {
+  @tracked isConnected = false;
+  @tracked userDisplayName = null;
+
+  oauthClient;
+
+  constructor() {
+    super(...arguments);
+
+    const clientId =
+      import.meta.env.VITE_OSM_CLIENT_ID || 'YOUR_CLIENT_ID_HERE';
+    const oauthUrl =
+      import.meta.env.VITE_OSM_OAUTH_URL || 'https://www.openstreetmap.org';
+
+    const redirectUrl =
+      import.meta.env.VITE_OSM_REDIRECT_URI ||
+      `${window.location.origin}/oauth/osm/callback`;
+
+    this.oauthClient = new OAuth2AuthCodePkceClient(
+      {
+        scopes: ['read_prefs', 'write_api'],
+        authorizationUrl: `${oauthUrl}/oauth2/authorize`,
+        tokenUrl: `${oauthUrl}/oauth2/token`,
+        clientId: clientId,
+        redirectUrl: redirectUrl,
+        storeRefreshToken: true,
+      },
+      new MarcoOsmAuthStorage()
+    );
+
+    this.restoreSession();
+  }
+
+  async restoreSession() {
+    const isAuthorized = await this.oauthClient.isAuthorized();
+    if (isAuthorized) {
+      this.isConnected = true;
+      const storedName = localStorage.getItem('marco:osm_user_display_name');
+      if (storedName) {
+        this.userDisplayName = storedName;
+      } else {
+        await this.fetchUserInfo();
+      }
+    }
+  }
+
+  async login() {
+    await this.oauthClient.requestAuthorizationCode();
+  }
+
+  async handleCallback() {
+    await this.oauthClient.receiveCode();
+    await this.oauthClient.getTokens();
+    this.isConnected = true;
+    await this.fetchUserInfo();
+  }
+
+  async logout() {
+    await this.oauthClient.reset();
+    this.isConnected = false;
+    this.userDisplayName = null;
+    localStorage.removeItem('marco:osm_user_display_name');
+  }
+
+  async fetchUserInfo() {
+    try {
+      const tokens = await this.oauthClient.getTokens();
+      // eslint-disable-next-line warp-drive/no-external-request-patterns
+      const response = await fetch(
+        'https://api.openstreetmap.org/api/0.6/user/details.json',
+        {
+          headers: {
+            Authorization: `Bearer ${tokens.accessToken}`,
+          },
+        }
+      );
+      if (response.ok) {
+        const data = await response.json();
+        console.debug('OSM data:', data);
+        const displayName = data.user.display_name;
+        this.userDisplayName = displayName;
+        localStorage.setItem('marco:osm_user_display_name', displayName);
+      } else {
+        console.error('Failed to fetch OSM user info', response.status);
+      }
+    } catch (e) {
+      console.error('Error fetching OSM user info', e);
+    }
+  }
+}
diff --git a/app/styles/app.css b/app/styles/app.css
index efa06f9..cde9263 100644
--- a/app/styles/app.css
+++ b/app/styles/app.css
@@ -246,6 +246,7 @@ body {
 
 .account-status {
   font-size: 0.85rem;
+  font-weight: bold;
   color: #898989;
   margin-top: 0.35rem;
   margin-left: calc(18px + 0.75rem);
diff --git a/package.json b/package.json
index 147bbe3..06eefb1 100644
--- a/package.json
+++ b/package.json
@@ -104,6 +104,7 @@
   "dependencies": {
     "@waysidemapping/pinhead": "^15.20.0",
     "ember-concurrency": "^5.2.0",
-    "ember-lifeline": "^7.0.0"
+    "ember-lifeline": "^7.0.0",
+    "oauth2-pkce": "^2.1.3"
   }
 }
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 7040a1b..62f2fe1 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -17,6 +17,9 @@ importers:
       ember-lifeline:
         specifier: ^7.0.0
         version: 7.0.0(@ember/test-helpers@5.4.1(@babel/core@7.28.6))
+      oauth2-pkce:
+        specifier: ^2.1.3
+        version: 2.1.3
     devDependencies:
       '@babel/core':
         specifier: ^7.28.5
@@ -4150,6 +4153,9 @@ packages:
   nwsapi@2.2.23:
     resolution: {integrity: sha512-7wfH4sLbt4M0gCDzGE6vzQBo0bfTKjU7Sfpqy/7gs1qBfYz2vEJH6vXcBKpO3+6Yu1telwd0t9HpyOoLEQQbIQ==}
 
+  oauth2-pkce@2.1.3:
+    resolution: {integrity: sha512-DcMiG5XUKNabf0qV1GOEPo+zwIdYsO2K1FMhiP8XnSCJbujZLOnSC5BCYiCtD0le+aue2fK6qDDvGjcQNF53jQ==}
+
   object-assign@4.1.1:
     resolution: {integrity: sha512-rJgTQnkUnH1sFw8yT6VSU3zD3sWmu6sZhIseY8VX+GRu3P6F7Fu+JNDoXfklElbLJSnc3FUQHVe4cU5hj+BcUg==}
     engines: {node: '>=0.10.0'}
@@ -10261,6 +10267,8 @@ snapshots:
 
   nwsapi@2.2.23: {}
 
+  oauth2-pkce@2.1.3: {}
+
   object-assign@4.1.1: {}
 
   object-hash@1.3.1: {}
diff --git a/tests/integration/components/user-menu-test.gjs b/tests/integration/components/user-menu-test.gjs
new file mode 100644
index 0000000..84483ae
--- /dev/null
+++ b/tests/integration/components/user-menu-test.gjs
@@ -0,0 +1,102 @@
+import { module, test } from 'qunit';
+import { setupRenderingTest } from 'marco/tests/helpers';
+import { render, click } from '@ember/test-helpers';
+import Service from '@ember/service';
+import { tracked } from '@glimmer/tracking';
+import UserMenu from 'marco/components/user-menu';
+
+class MockOsmAuthService extends Service {
+  @tracked isConnected = false;
+  @tracked userDisplayName = null;
+
+  loginCalled = false;
+  logoutCalled = false;
+
+  login() {
+    this.loginCalled = true;
+  }
+
+  logout() {
+    this.logoutCalled = true;
+  }
+}
+
+class MockStorageService extends Service {
+  @tracked connected = false;
+  @tracked userAddress = null;
+}
+
+module('Integration | Component | user-menu', function (hooks) {
+  setupRenderingTest(hooks);
+
+  hooks.beforeEach(function () {
+    this.owner.register('service:osmAuth', MockOsmAuthService);
+    this.owner.register('service:storage', MockStorageService);
+    this.osmAuth = this.owner.lookup('service:osmAuth');
+  });
+
+  test('it renders disconnected OSM state correctly', async function (assert) {
+    this.osmAuth.isConnected = false;
+
+    this.storageArg = {
+      connected: false,
+      userAddress: null,
+    };
+    this.onClose = () => {};
+
+    await render(
+      <template>
+        <UserMenu @storage={{this.storageArg}} @onClose={{this.onClose}} />
+      </template>
+    );
+
+    assert
+      .dom('.account-list .account-item:nth-child(2) .account-info')
+      .includesText('OpenStreetMap');
+    assert
+      .dom('.account-list .account-item:nth-child(2) button')
+      .hasText('Connect');
+    assert
+      .dom('.account-list .account-item:nth-child(2) .account-status')
+      .hasText('Not connected');
+
+    await click('.account-list .account-item:nth-child(2) button');
+    assert.true(
+      this.osmAuth.loginCalled,
+      'osmAuth.login() was called when Connect is clicked'
+    );
+  });
+
+  test('it renders connected OSM state correctly', async function (assert) {
+    this.osmAuth.isConnected = true;
+    this.osmAuth.userDisplayName = 'TestMapper';
+
+    this.storageArg = {
+      connected: false,
+      userAddress: null,
+    };
+    this.onClose = () => {};
+
+    await render(
+      <template>
+        <UserMenu @storage={{this.storageArg}} @onClose={{this.onClose}} />
+      </template>
+    );
+
+    assert
+      .dom('.account-list .account-item:nth-child(2) .account-info')
+      .includesText('OpenStreetMap');
+    assert
+      .dom('.account-list .account-item:nth-child(2) button')
+      .hasText('Disconnect');
+    assert
+      .dom('.account-list .account-item:nth-child(2) .account-status')
+      .hasText('TestMapper');
+
+    await click('.account-list .account-item:nth-child(2) button');
+    assert.true(
+      this.osmAuth.logoutCalled,
+      'osmAuth.logout() was called when Disconnect is clicked'
+    );
+  });
+});
diff --git a/tests/unit/routes/oauth/osm-callback-test.js b/tests/unit/routes/oauth/osm-callback-test.js
new file mode 100644
index 0000000..78252b4
--- /dev/null
+++ b/tests/unit/routes/oauth/osm-callback-test.js
@@ -0,0 +1,47 @@
+import { module, test } from 'qunit';
+import { setupTest } from 'marco/tests/helpers';
+import Service from '@ember/service';
+
+class MockOsmAuthService extends Service {
+  handleCallbackCalled = false;
+
+  async handleCallback() {
+    this.handleCallbackCalled = true;
+    return Promise.resolve();
+  }
+}
+
+class MockRouterService extends Service {
+  transitionToArgs = [];
+
+  transitionTo(...args) {
+    this.transitionToArgs.push(args);
+  }
+}
+
+module('Unit | Route | oauth/osm-callback', function (hooks) {
+  setupTest(hooks);
+
+  hooks.beforeEach(function () {
+    this.owner.register('service:osmAuth', MockOsmAuthService);
+    this.owner.register('service:router', MockRouterService);
+  });
+
+  test('it handles the callback and transitions to index', async function (assert) {
+    let route = this.owner.lookup('route:oauth/osm-callback');
+    let osmAuth = this.owner.lookup('service:osmAuth');
+    let router = this.owner.lookup('service:router');
+
+    await route.model();
+
+    assert.true(
+      osmAuth.handleCallbackCalled,
+      'handleCallback was called on the osmAuth service'
+    );
+    assert.deepEqual(
+      router.transitionToArgs,
+      [['index']],
+      'router transitioned back to index route'
+    );
+  });
+});
diff --git a/tests/unit/services/osm-auth-test.js b/tests/unit/services/osm-auth-test.js
new file mode 100644
index 0000000..b860dcc
--- /dev/null
+++ b/tests/unit/services/osm-auth-test.js
@@ -0,0 +1,156 @@
+import { module, test } from 'qunit';
+import { setupTest } from 'marco/tests/helpers';
+
+module('Unit | Service | osm-auth', function (hooks) {
+  setupTest(hooks);
+
+  let originalLocalStorage;
+  let originalFetch;
+
+  hooks.beforeEach(function () {
+    // Stub localStorage
+    let mockStorage = {};
+    originalLocalStorage = window.localStorage;
+
+    Object.defineProperty(window, 'localStorage', {
+      value: {
+        getItem: (key) => mockStorage[key] || null,
+        setItem: (key, value) => {
+          mockStorage[key] = value.toString();
+        },
+        removeItem: (key) => {
+          delete mockStorage[key];
+        },
+        clear: () => {
+          mockStorage = {};
+        },
+      },
+      writable: true,
+    });
+
+    // Stub fetch
+    originalFetch = window.fetch;
+    window.fetch = async () => {
+      return {
+        ok: true,
+        json: async () => ({
+          user: { display_name: 'MockedUser' },
+        }),
+      };
+    };
+  });
+
+  hooks.afterEach(function () {
+    window.localStorage = originalLocalStorage;
+    window.fetch = originalFetch;
+  });
+
+  test('it restores session correctly when logged in', async function (assert) {
+    let service = this.owner.factoryFor('service:osm-auth').create();
+
+    // Stub the underlying oauthClient before it runs restoreSession (actually restoreSession runs in constructor, so we need to intercept it)
+    // Because restoreSession runs in the constructor, we might need to overwrite it after, but it's async.
+    // Let's just create it, let the original restoreSession fail or do nothing, and then we stub and re-call it.
+
+    service.oauthClient.isAuthorized = async () => true;
+    window.localStorage.setItem('marco:osm_user_display_name', 'CachedName');
+
+    await service.restoreSession();
+
+    assert.true(service.isConnected, 'Service becomes connected');
+    assert.strictEqual(
+      service.userDisplayName,
+      'CachedName',
+      'Restores name from localStorage'
+    );
+  });
+
+  test('it fetches user info when logged in but no cached name', async function (assert) {
+    let service = this.owner.factoryFor('service:osm-auth').create();
+
+    service.oauthClient.isAuthorized = async () => true;
+    service.oauthClient.getTokens = async () => ({ accessToken: 'fake-token' });
+    // Ensure localStorage is empty for this key
+    window.localStorage.removeItem('marco:osm_user_display_name');
+
+    await service.restoreSession();
+
+    assert.true(service.isConnected, 'Service becomes connected');
+    assert.strictEqual(
+      service.userDisplayName,
+      'MockedUser',
+      'Fetched name from API'
+    );
+    assert.strictEqual(
+      window.localStorage.getItem('marco:osm_user_display_name'),
+      'MockedUser',
+      'Saved name to localStorage'
+    );
+  });
+
+  test('it handles login()', async function (assert) {
+    let service = this.owner.lookup('service:osm-auth');
+    let requestCalled = false;
+    service.oauthClient.requestAuthorizationCode = async () => {
+      requestCalled = true;
+    };
+
+    await service.login();
+    assert.true(
+      requestCalled,
+      'Delegates to oauthClient.requestAuthorizationCode()'
+    );
+  });
+
+  test('it handles logout()', async function (assert) {
+    let service = this.owner.lookup('service:osm-auth');
+    service.isConnected = true;
+    service.userDisplayName = 'ToBeCleared';
+    window.localStorage.setItem('marco:osm_user_display_name', 'ToBeCleared');
+
+    let resetCalled = false;
+    service.oauthClient.reset = async () => {
+      resetCalled = true;
+    };
+
+    await service.logout();
+
+    assert.true(resetCalled, 'Delegates to oauthClient.reset()');
+    assert.false(service.isConnected, 'isConnected is reset');
+    assert.strictEqual(
+      service.userDisplayName,
+      null,
+      'userDisplayName is reset'
+    );
+    assert.strictEqual(
+      window.localStorage.getItem('marco:osm_user_display_name'),
+      null,
+      'localStorage is cleared'
+    );
+  });
+
+  test('it handles the callback flow', async function (assert) {
+    let service = this.owner.lookup('service:osm-auth');
+    let receiveCodeCalled = false;
+    let getTokensCalled = false;
+
+    service.oauthClient.receiveCode = async () => {
+      receiveCodeCalled = true;
+    };
+    service.oauthClient.getTokens = async () => {
+      getTokensCalled = true;
+      return { accessToken: 'fake-token' };
+    };
+
+    await service.handleCallback();
+
+    assert.true(receiveCodeCalled, 'oauthClient.receiveCode was called');
+    assert.true(getTokensCalled, 'oauthClient.getTokens was called');
+    assert.true(service.isConnected, 'Service is connected after callback');
+    assert.strictEqual(
+      service.userDisplayName,
+      'MockedUser',
+      'User info fetched and set during callback'
+    );
+  });
+});
diff --git a/vite.config.mjs b/vite.config.mjs
index 27beb86..0d95c21 100644
--- a/vite.config.mjs
+++ b/vite.config.mjs
@@ -3,9 +3,9 @@ import { extensions, ember } from '@embroider/vite';
 import { babel } from '@rollup/plugin-babel';
 
 export default defineConfig({
-  // server: {
-  //   host: '0.0.0.0',
-  // },
+  server: {
+    host: '127.0.0.1',
+  },
   plugins: [
     ember(),
     // extra plugins here