diff --git a/.changeset/ninety-jeans-scream.md b/.changeset/ninety-jeans-scream.md
new file mode 100644
index 0000000000..3465a67444
--- /dev/null
+++ b/.changeset/ninety-jeans-scream.md
@@ -0,0 +1,5 @@
+---
+'@backstage/errors': minor
+---
+
+Added `ServiceUnavailableError`
diff --git a/.changeset/tasty-oranges-sleep.md b/.changeset/tasty-oranges-sleep.md
new file mode 100644
index 0000000000..7c99ecc822
--- /dev/null
+++ b/.changeset/tasty-oranges-sleep.md
@@ -0,0 +1,5 @@
+---
+'@backstage/backend-app-api': patch
+---
+
+Added handling of `ServiceUnavailableError` to error handling middleware.
diff --git a/packages/backend-app-api/src/http/MiddlewareFactory.test.ts b/packages/backend-app-api/src/http/MiddlewareFactory.test.ts
index 64812564ca..5dbb63ec59 100644
--- a/packages/backend-app-api/src/http/MiddlewareFactory.test.ts
+++ b/packages/backend-app-api/src/http/MiddlewareFactory.test.ts
@@ -21,6 +21,7 @@ import {
   NotAllowedError,
   NotFoundError,
   NotModifiedError,
+  ServiceUnavailableError,
 } from '@backstage/errors';
 import express from 'express';
 import createError from 'http-errors';
@@ -143,6 +144,9 @@ describe('MiddlewareFactory', () => {
       app.use('/ConflictError', () => {
         throw new ConflictError();
       });
+      app.use('/ServiceUnavailableError', () => {
+        throw new ServiceUnavailableError();
+      });
       app.use(middleware.error());
 
       const r = request(app);
@@ -165,6 +169,10 @@ describe('MiddlewareFactory', () => {
       expect((await r.get('/ConflictError')).body.error.name).toBe(
         'ConflictError',
       );
+      expect((await r.get('/ServiceUnavailableError')).status).toBe(503);
+      expect((await r.get('/ServiceUnavailableError')).body.error.name).toBe(
+        'ServiceUnavailableError',
+      );
     });
 
     it('logs all 500 errors', async () => {
diff --git a/packages/backend-app-api/src/http/MiddlewareFactory.ts b/packages/backend-app-api/src/http/MiddlewareFactory.ts
index 833bdba540..774e784d1d 100644
--- a/packages/backend-app-api/src/http/MiddlewareFactory.ts
+++ b/packages/backend-app-api/src/http/MiddlewareFactory.ts
@@ -36,6 +36,7 @@ import {
   NotAllowedError,
   NotFoundError,
   NotModifiedError,
+  ServiceUnavailableError,
   serializeError,
 } from '@backstage/errors';
 import { NotImplementedError } from '@backstage/errors';
@@ -260,6 +261,8 @@ function getStatusCode(error: Error): number {
       return 409;
     case NotImplementedError.name:
       return 501;
+    case ServiceUnavailableError.name:
+      return 503;
     default:
       break;
   }
diff --git a/packages/errors/api-report.md b/packages/errors/api-report.md
index 650a826a30..0d405d8ba6 100644
--- a/packages/errors/api-report.md
+++ b/packages/errors/api-report.md
@@ -125,6 +125,9 @@ export function serializeError(
   },
 ): SerializedError;
 
+// @public
+export class ServiceUnavailableError extends CustomErrorBase {}
+
 // @public
 export function stringifyError(error: unknown): string;
 ```
diff --git a/packages/errors/src/errors/common.ts b/packages/errors/src/errors/common.ts
index e1a292d7b5..a2ea20e99f 100644
--- a/packages/errors/src/errors/common.ts
+++ b/packages/errors/src/errors/common.ts
@@ -81,6 +81,13 @@ export class NotModifiedError extends CustomErrorBase {}
  */
 export class NotImplementedError extends CustomErrorBase {}
 
+/**
+ * The server is not ready to handle the request.
+ *
+ * @public
+ */
+export class ServiceUnavailableError extends CustomErrorBase {}
+
 /**
  * An error that forwards an underlying cause with additional context in the message.
  *
diff --git a/packages/errors/src/errors/index.ts b/packages/errors/src/errors/index.ts
index efd3257fbf..0a59891f87 100644
--- a/packages/errors/src/errors/index.ts
+++ b/packages/errors/src/errors/index.ts
@@ -25,6 +25,7 @@ export {
   NotFoundError,
   NotModifiedError,
   NotImplementedError,
+  ServiceUnavailableError,
 } from './common';
 export { CustomErrorBase } from './CustomErrorBase';
 export { ResponseError } from './ResponseError';