diff --git a/.changeset/eleven-donuts-bathe.md b/.changeset/eleven-donuts-bathe.md
new file mode 100644
index 0000000000..3eb33b087d
--- /dev/null
+++ b/.changeset/eleven-donuts-bathe.md
@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-auth-backend': minor
+---
+
+Switched the handling of the `BackstageIdentityResponse` so that the returned `identity.userEntityRef` is always a full entity reference. If `userEntityRef` was previously set to `jane`, it will now be `user:default/jane`. The `userEntityRef` in the response is parsed from the `sub` claim in the payload of the Backstage token.
diff --git a/plugins/auth-backend/src/lib/oauth/OAuthAdapter.test.ts b/plugins/auth-backend/src/lib/oauth/OAuthAdapter.test.ts
index 98f4cd9fa1..a7463bb7dc 100644
--- a/plugins/auth-backend/src/lib/oauth/OAuthAdapter.test.ts
+++ b/plugins/auth-backend/src/lib/oauth/OAuthAdapter.test.ts
@@ -233,7 +233,7 @@ describe('OAuthAdapter', () => {
         identity: {
           ownershipEntityRefs: ['user:default/jimmymarkum'],
           type: 'user',
-          userEntityRef: 'jimmymarkum',
+          userEntityRef: 'user:default/jimmymarkum',
         },
       },
     });
diff --git a/plugins/auth-backend/src/providers/aws-alb/provider.test.ts b/plugins/auth-backend/src/providers/aws-alb/provider.test.ts
index fd5fe28505..37b5bc1f68 100644
--- a/plugins/auth-backend/src/providers/aws-alb/provider.test.ts
+++ b/plugins/auth-backend/src/providers/aws-alb/provider.test.ts
@@ -144,7 +144,7 @@ describe('AwsAlbAuthProvider', () => {
           identity: {
             ownershipEntityRefs: ['user:default/jimmymarkum'],
             type: 'user',
-            userEntityRef: 'jimmymarkum',
+            userEntityRef: 'user:default/jimmymarkum',
           },
         },
         profile: {
diff --git a/plugins/auth-backend/src/providers/oauth2-proxy/provider.test.ts b/plugins/auth-backend/src/providers/oauth2-proxy/provider.test.ts
index 4e1aeb88bf..048a3b9344 100644
--- a/plugins/auth-backend/src/providers/oauth2-proxy/provider.test.ts
+++ b/plugins/auth-backend/src/providers/oauth2-proxy/provider.test.ts
@@ -167,7 +167,7 @@ describe('Oauth2ProxyAuthProvider', () => {
           identity: {
             ownershipEntityRefs: ['user:default/jimmymarkum'],
             type: 'user',
-            userEntityRef: 'jimmymarkum',
+            userEntityRef: 'user:default/jimmymarkum',
           },
           token: mockToken,
         },
diff --git a/plugins/auth-backend/src/providers/prepareBackstageIdentityResponse.test.ts b/plugins/auth-backend/src/providers/prepareBackstageIdentityResponse.test.ts
new file mode 100644
index 0000000000..24442379c4
--- /dev/null
+++ b/plugins/auth-backend/src/providers/prepareBackstageIdentityResponse.test.ts
@@ -0,0 +1,107 @@
+/*
+ * Copyright 2020 The Backstage Authors
+ *
+ * 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 { prepareBackstageIdentityResponse } from './prepareBackstageIdentityResponse';
+
+function mkToken(payload: unknown) {
+  return `a.${Buffer.from(JSON.stringify(payload), 'utf8').toString(
+    'base64',
+  )}.z`;
+}
+
+describe('prepareBackstageIdentityResponse', () => {
+  it('parses a complete token to determine the identity', () => {
+    const token = mkToken({ sub: 'k:ns/n', ent: ['k:ns/o'] });
+    expect(
+      prepareBackstageIdentityResponse({
+        id: 'x',
+        token,
+      }),
+    ).toEqual({
+      id: 'x',
+      token,
+      idToken: token,
+      identity: {
+        type: 'user',
+        userEntityRef: 'k:ns/n',
+        ownershipEntityRefs: ['k:ns/o'],
+      },
+    });
+  });
+
+  it('populates incomplete identities', () => {
+    expect(
+      prepareBackstageIdentityResponse({
+        id: 'x',
+        token: mkToken({ sub: 'n' }),
+      }),
+    ).toEqual({
+      id: 'x',
+      token: expect.any(String),
+      idToken: expect.any(String),
+      identity: {
+        type: 'user',
+        userEntityRef: 'user:default/n',
+        ownershipEntityRefs: [],
+      },
+    });
+    expect(
+      prepareBackstageIdentityResponse({
+        id: 'x',
+        token: mkToken({ sub: 'k:n' }),
+      }),
+    ).toEqual({
+      id: 'x',
+      token: expect.any(String),
+      idToken: expect.any(String),
+      identity: {
+        type: 'user',
+        userEntityRef: 'k:default/n',
+        ownershipEntityRefs: [],
+      },
+    });
+    expect(
+      prepareBackstageIdentityResponse({
+        id: 'x',
+        token: mkToken({ sub: 'ns/n' }),
+      }),
+    ).toEqual({
+      id: 'x',
+      token: expect.any(String),
+      idToken: expect.any(String),
+      identity: {
+        type: 'user',
+        userEntityRef: 'user:ns/n',
+        ownershipEntityRefs: [],
+      },
+    });
+    expect(
+      prepareBackstageIdentityResponse({
+        id: 'x',
+        token: mkToken({ sub: 'n', ent: ['k:ns/o'] }),
+      }),
+    ).toEqual({
+      id: 'x',
+      token: expect.any(String),
+      idToken: expect.any(String),
+      identity: {
+        type: 'user',
+        userEntityRef: 'user:default/n',
+        ownershipEntityRefs: ['k:ns/o'],
+      },
+    });
+  });
+});
diff --git a/plugins/auth-backend/src/providers/prepareBackstageIdentityResponse.ts b/plugins/auth-backend/src/providers/prepareBackstageIdentityResponse.ts
index 1de8ebb9b2..bb99cb3487 100644
--- a/plugins/auth-backend/src/providers/prepareBackstageIdentityResponse.ts
+++ b/plugins/auth-backend/src/providers/prepareBackstageIdentityResponse.ts
@@ -14,6 +14,11 @@
  * limitations under the License.
  */
 
+import {
+  ENTITY_DEFAULT_NAMESPACE,
+  parseEntityRef,
+  stringifyEntityRef,
+} from '@backstage/catalog-model';
 import { BackstageIdentityResponse, BackstageSignInResult } from './types';
 
 function parseJwtPayload(token: string) {
@@ -32,6 +37,13 @@ export function prepareBackstageIdentityResponse(
   result: BackstageSignInResult,
 ): BackstageIdentityResponse {
   const { sub, ent } = parseJwtPayload(result.token);
+
+  const userEntityRef = stringifyEntityRef(
+    parseEntityRef(sub, {
+      defaultKind: 'user',
+      defaultNamespace: ENTITY_DEFAULT_NAMESPACE,
+    }),
+  );
   return {
     ...{
       // TODO: idToken is for backwards compatibility and can be removed in the future
@@ -40,7 +52,7 @@ export function prepareBackstageIdentityResponse(
     },
     identity: {
       type: 'user',
-      userEntityRef: sub,
+      userEntityRef,
       ownershipEntityRefs: ent ?? [],
     },
   };