diff --git a/homeassistant/auth/providers/homeassistant.py b/homeassistant/auth/providers/homeassistant.py
index 2c5a76d2c90..f5605886628 100644
--- a/homeassistant/auth/providers/homeassistant.py
+++ b/homeassistant/auth/providers/homeassistant.py
@@ -1,6 +1,7 @@
 """Home Assistant auth provider."""
 import base64
 from collections import OrderedDict
+import logging
 from typing import Any, Dict, List, Optional, cast
 
 import bcrypt
@@ -51,6 +52,15 @@ class Data:
         self._store = hass.helpers.storage.Store(STORAGE_VERSION, STORAGE_KEY,
                                                  private=True)
         self._data = None  # type: Optional[Dict[str, Any]]
+        self.is_legacy = False
+
+    @callback
+    def normalize_username(self, username: str) -> str:
+        """Normalize a username based on the mode."""
+        if self.is_legacy:
+            return username
+
+        return username.strip()
 
     async def async_load(self) -> None:
         """Load stored data."""
@@ -61,6 +71,20 @@ class Data:
                 'users': []
             }
 
+        for user in data['users']:
+            username = user['username']
+
+            # check if we have unstripped usernames
+            if username != username.strip():
+                self.is_legacy = True
+
+                logging.getLogger(__name__).warning(
+                    "Home Assistant auth provider is running in legacy mode "
+                    "because we detected usernames that start or end in a "
+                    "space. Please change the username.")
+
+                break
+
         self._data = data
 
     @property
@@ -73,6 +97,7 @@ class Data:
 
         Raises InvalidAuth if auth invalid.
         """
+        username = self.normalize_username(username)
         dummy = b'$2b$12$CiuFGszHx9eNHxPuQcwBWez4CwDTOcLTX5CbOpV6gef2nYuXkY7BO'
         found = None
 
@@ -105,7 +130,10 @@ class Data:
 
     def add_auth(self, username: str, password: str) -> None:
         """Add a new authenticated user/pass."""
-        if any(user['username'] == username for user in self.users):
+        username = self.normalize_username(username)
+
+        if any(self.normalize_username(user['username']) == username
+               for user in self.users):
             raise InvalidUser
 
         self.users.append({
@@ -116,9 +144,11 @@ class Data:
     @callback
     def async_remove_auth(self, username: str) -> None:
         """Remove authentication."""
+        username = self.normalize_username(username)
+
         index = None
         for i, user in enumerate(self.users):
-            if user['username'] == username:
+            if self.normalize_username(user['username']) == username:
                 index = i
                 break
 
@@ -132,8 +162,10 @@ class Data:
 
         Raises InvalidUser if user cannot be found.
         """
+        username = self.normalize_username(username)
+
         for user in self.users:
-            if user['username'] == username:
+            if self.normalize_username(user['username']) == username:
                 user['password'] = self.hash_password(
                     new_password, True).decode()
                 break
@@ -178,10 +210,15 @@ class HassAuthProvider(AuthProvider):
     async def async_get_or_create_credentials(
             self, flow_result: Dict[str, str]) -> Credentials:
         """Get credentials based on the flow result."""
-        username = flow_result['username']
+        if self.data is None:
+            await self.async_initialize()
+            assert self.data is not None
+
+        norm_username = self.data.normalize_username
+        username = norm_username(flow_result['username'])
 
         for credential in await self.async_credentials():
-            if credential.data['username'] == username:
+            if norm_username(credential.data['username']) == username:
                 return credential
 
         # Create new credentials.
diff --git a/tests/auth/providers/test_homeassistant.py b/tests/auth/providers/test_homeassistant.py
index d3fa27b9f5b..b654b42fb35 100644
--- a/tests/auth/providers/test_homeassistant.py
+++ b/tests/auth/providers/test_homeassistant.py
@@ -1,5 +1,5 @@
 """Test the Home Assistant local auth provider."""
-from unittest.mock import Mock
+from unittest.mock import Mock, patch
 
 import pytest
 import voluptuous as vol
@@ -9,6 +9,8 @@ from homeassistant.auth import auth_manager_from_config, auth_store
 from homeassistant.auth.providers import (
     auth_provider_from_config, homeassistant as hass_auth)
 
+from tests.common import mock_coro
+
 
 @pytest.fixture
 def data(hass):
@@ -18,17 +20,13 @@ def data(hass):
     return data
 
 
-async def test_adding_user(data, hass):
-    """Test adding a user."""
-    data.add_auth('test-user', 'test-pass')
-    data.validate_login('test-user', 'test-pass')
-
-
-async def test_adding_user_duplicate_username(data, hass):
-    """Test adding a user with duplicate username."""
-    data.add_auth('test-user', 'test-pass')
-    with pytest.raises(hass_auth.InvalidUser):
-        data.add_auth('test-user', 'other-pass')
+@pytest.fixture
+def legacy_data(hass):
+    """Create a loaded legacy data class."""
+    data = hass_auth.Data(hass)
+    hass.loop.run_until_complete(data.async_load())
+    data.is_legacy = True
+    return data
 
 
 async def test_validating_password_invalid_user(data, hass):
@@ -37,30 +35,72 @@ async def test_validating_password_invalid_user(data, hass):
         data.validate_login('non-existing', 'pw')
 
 
+async def test_not_allow_set_id():
+    """Test we are not allowed to set an ID in config."""
+    hass = Mock()
+    with pytest.raises(vol.Invalid):
+        await auth_provider_from_config(hass, None, {
+            'type': 'homeassistant',
+            'id': 'invalid',
+        })
+
+
+async def test_new_users_populate_values(hass, data):
+    """Test that we populate data for new users."""
+    data.add_auth('hello', 'test-pass')
+    await data.async_save()
+
+    manager = await auth_manager_from_config(hass, [{
+        'type': 'homeassistant'
+    }], [])
+    provider = manager.auth_providers[0]
+    credentials = await provider.async_get_or_create_credentials({
+        'username': 'hello'
+    })
+    user = await manager.async_get_or_create_user(credentials)
+    assert user.name == 'hello'
+    assert user.is_active
+
+
+async def test_changing_password_raises_invalid_user(data, hass):
+    """Test that changing password raises invalid user."""
+    with pytest.raises(hass_auth.InvalidUser):
+        data.change_password('non-existing', 'pw')
+
+
+# Modern mode
+
+async def test_adding_user(data, hass):
+    """Test adding a user."""
+    data.add_auth('test-user', 'test-pass')
+    data.validate_login('test-user', 'test-pass')
+    data.validate_login(' test-user ', 'test-pass')
+
+
+async def test_adding_user_duplicate_username(data, hass):
+    """Test adding a user with duplicate username."""
+    data.add_auth('test-user', 'test-pass')
+    with pytest.raises(hass_auth.InvalidUser):
+        data.add_auth('test-user ', 'other-pass')
+
+
 async def test_validating_password_invalid_password(data, hass):
     """Test validating an invalid password."""
     data.add_auth('test-user', 'test-pass')
 
     with pytest.raises(hass_auth.InvalidAuth):
-        data.validate_login('test-user', 'invalid-pass')
+        data.validate_login(' test-user ', 'invalid-pass')
 
 
 async def test_changing_password(data, hass):
     """Test adding a user."""
-    user = 'test-user'
-    data.add_auth(user, 'test-pass')
-    data.change_password(user, 'new-pass')
+    data.add_auth('test-user', 'test-pass')
+    data.change_password('test-user ', 'new-pass')
 
     with pytest.raises(hass_auth.InvalidAuth):
-        data.validate_login(user, 'test-pass')
+        data.validate_login('test-user', 'test-pass')
 
-    data.validate_login(user, 'new-pass')
-
-
-async def test_changing_password_raises_invalid_user(data, hass):
-    """Test that we initialize an empty config."""
-    with pytest.raises(hass_auth.InvalidUser):
-        data.change_password('non-existing', 'pw')
+    data.validate_login('test-user', 'new-pass')
 
 
 async def test_login_flow_validates(data, hass):
@@ -81,6 +121,110 @@ async def test_login_flow_validates(data, hass):
     assert result['type'] == data_entry_flow.RESULT_TYPE_FORM
     assert result['errors']['base'] == 'invalid_auth'
 
+    result = await flow.async_step_init({
+        'username': 'test-user ',
+        'password': 'incorrect-pass',
+    })
+    assert result['type'] == data_entry_flow.RESULT_TYPE_FORM
+    assert result['errors']['base'] == 'invalid_auth'
+
+    result = await flow.async_step_init({
+        'username': 'test-user',
+        'password': 'test-pass',
+    })
+    assert result['type'] == data_entry_flow.RESULT_TYPE_CREATE_ENTRY
+    assert result['data']['username'] == 'test-user'
+
+
+async def test_saving_loading(data, hass):
+    """Test saving and loading JSON."""
+    data.add_auth('test-user', 'test-pass')
+    data.add_auth('second-user', 'second-pass')
+    await data.async_save()
+
+    data = hass_auth.Data(hass)
+    await data.async_load()
+    data.validate_login('test-user ', 'test-pass')
+    data.validate_login('second-user ', 'second-pass')
+
+
+async def test_get_or_create_credentials(hass, data):
+    """Test that we can get or create credentials."""
+    manager = await auth_manager_from_config(hass, [{
+        'type': 'homeassistant'
+    }], [])
+    provider = manager.auth_providers[0]
+    provider.data = data
+    credentials1 = await provider.async_get_or_create_credentials({
+        'username': 'hello'
+    })
+    with patch.object(provider, 'async_credentials',
+                      return_value=mock_coro([credentials1])):
+        credentials2 = await provider.async_get_or_create_credentials({
+            'username': 'hello '
+        })
+    assert credentials1 is credentials2
+
+
+# Legacy mode
+
+async def test_legacy_adding_user(legacy_data, hass):
+    """Test in legacy mode adding a user."""
+    legacy_data.add_auth('test-user', 'test-pass')
+    legacy_data.validate_login('test-user', 'test-pass')
+
+
+async def test_legacy_adding_user_duplicate_username(legacy_data, hass):
+    """Test in legacy mode adding a user with duplicate username."""
+    legacy_data.add_auth('test-user', 'test-pass')
+    with pytest.raises(hass_auth.InvalidUser):
+        legacy_data.add_auth('test-user', 'other-pass')
+
+
+async def test_legacy_validating_password_invalid_password(legacy_data, hass):
+    """Test in legacy mode validating an invalid password."""
+    legacy_data.add_auth('test-user', 'test-pass')
+
+    with pytest.raises(hass_auth.InvalidAuth):
+        legacy_data.validate_login('test-user', 'invalid-pass')
+
+
+async def test_legacy_changing_password(legacy_data, hass):
+    """Test in legacy mode adding a user."""
+    user = 'test-user'
+    legacy_data.add_auth(user, 'test-pass')
+    legacy_data.change_password(user, 'new-pass')
+
+    with pytest.raises(hass_auth.InvalidAuth):
+        legacy_data.validate_login(user, 'test-pass')
+
+    legacy_data.validate_login(user, 'new-pass')
+
+
+async def test_legacy_changing_password_raises_invalid_user(legacy_data, hass):
+    """Test in legacy mode that we initialize an empty config."""
+    with pytest.raises(hass_auth.InvalidUser):
+        legacy_data.change_password('non-existing', 'pw')
+
+
+async def test_legacy_login_flow_validates(legacy_data, hass):
+    """Test in legacy mode login flow."""
+    legacy_data.add_auth('test-user', 'test-pass')
+    await legacy_data.async_save()
+
+    provider = hass_auth.HassAuthProvider(hass, auth_store.AuthStore(hass),
+                                          {'type': 'homeassistant'})
+    flow = await provider.async_login_flow({})
+    result = await flow.async_step_init()
+    assert result['type'] == data_entry_flow.RESULT_TYPE_FORM
+
+    result = await flow.async_step_init({
+        'username': 'incorrect-user',
+        'password': 'test-pass',
+    })
+    assert result['type'] == data_entry_flow.RESULT_TYPE_FORM
+    assert result['errors']['base'] == 'invalid_auth'
+
     result = await flow.async_step_init({
         'username': 'test-user',
         'password': 'incorrect-pass',
@@ -96,40 +240,43 @@ async def test_login_flow_validates(data, hass):
     assert result['data']['username'] == 'test-user'
 
 
-async def test_saving_loading(data, hass):
-    """Test saving and loading JSON."""
-    data.add_auth('test-user', 'test-pass')
-    data.add_auth('second-user', 'second-pass')
-    await data.async_save()
+async def test_legacy_saving_loading(legacy_data, hass):
+    """Test in legacy mode saving and loading JSON."""
+    legacy_data.add_auth('test-user', 'test-pass')
+    legacy_data.add_auth('second-user', 'second-pass')
+    await legacy_data.async_save()
 
-    data = hass_auth.Data(hass)
-    await data.async_load()
-    data.validate_login('test-user', 'test-pass')
-    data.validate_login('second-user', 'second-pass')
+    legacy_data = hass_auth.Data(hass)
+    await legacy_data.async_load()
+    legacy_data.is_legacy = True
+    legacy_data.validate_login('test-user', 'test-pass')
+    legacy_data.validate_login('second-user', 'second-pass')
+
+    with pytest.raises(hass_auth.InvalidAuth):
+        legacy_data.validate_login('test-user ', 'test-pass')
 
 
-async def test_not_allow_set_id():
-    """Test we are not allowed to set an ID in config."""
-    hass = Mock()
-    with pytest.raises(vol.Invalid):
-        await auth_provider_from_config(hass, None, {
-            'type': 'homeassistant',
-            'id': 'invalid',
-        })
-
-
-async def test_new_users_populate_values(hass, data):
-    """Test that we populate data for new users."""
-    data.add_auth('hello', 'test-pass')
-    await data.async_save()
-
+async def test_legacy_get_or_create_credentials(hass, legacy_data):
+    """Test in legacy mode that we can get or create credentials."""
     manager = await auth_manager_from_config(hass, [{
         'type': 'homeassistant'
     }], [])
     provider = manager.auth_providers[0]
-    credentials = await provider.async_get_or_create_credentials({
+    provider.data = legacy_data
+    credentials1 = await provider.async_get_or_create_credentials({
         'username': 'hello'
     })
-    user = await manager.async_get_or_create_user(credentials)
-    assert user.name == 'hello'
-    assert user.is_active
+
+    with patch.object(provider, 'async_credentials',
+                      return_value=mock_coro([credentials1])):
+        credentials2 = await provider.async_get_or_create_credentials({
+            'username': 'hello'
+        })
+    assert credentials1 is credentials2
+
+    with patch.object(provider, 'async_credentials',
+                      return_value=mock_coro([credentials1])):
+        credentials3 = await provider.async_get_or_create_credentials({
+            'username': 'hello '
+        })
+    assert credentials1 is not credentials3
diff --git a/tests/components/config/test_auth_provider_homeassistant.py b/tests/components/config/test_auth_provider_homeassistant.py
index a4c4c5a3c5a..4cbf3493a93 100644
--- a/tests/components/config/test_auth_provider_homeassistant.py
+++ b/tests/components/config/test_auth_provider_homeassistant.py
@@ -168,10 +168,6 @@ async def test_delete_removes_credential(hass, hass_ws_client,
     client = await hass_ws_client(hass, hass_access_token)
 
     user = MockUser().add_to_hass(hass)
-    user.credentials.append(
-        await hass.auth.auth_providers[0].async_get_or_create_credentials({
-            'username': 'test-user'}))
-
     hass_storage[prov_ha.STORAGE_KEY] = {
         'version': 1,
         'data': {
@@ -181,6 +177,10 @@ async def test_delete_removes_credential(hass, hass_ws_client,
         }
     }
 
+    user.credentials.append(
+        await hass.auth.auth_providers[0].async_get_or_create_credentials({
+            'username': 'test-user'}))
+
     await client.send_json({
         'id': 5,
         'type': auth_ha.WS_TYPE_DELETE,