diff --git a/.changeset/fix-aws-s3-url-reader-custom-endpoints.md b/.changeset/fix-aws-s3-url-reader-custom-endpoints.md
new file mode 100644
index 0000000000..c9fe3923ba
--- /dev/null
+++ b/.changeset/fix-aws-s3-url-reader-custom-endpoints.md
@@ -0,0 +1,5 @@
+---
+'@backstage/backend-defaults': patch
+---
+
+Fixed `AwsS3UrlReader` failing to read files from S3 buckets configured with custom endpoint hosts. When an integration was configured with a specific endpoint like `https://bucket-1.s3.eu-central-1.amazonaws.com`, the URL parser incorrectly fell through to the non-AWS code path, always defaulting the region to `us-east-1` instead of extracting it from the hostname.
diff --git a/packages/backend-defaults/src/entrypoints/urlReader/lib/AwsS3UrlReader.test.ts b/packages/backend-defaults/src/entrypoints/urlReader/lib/AwsS3UrlReader.test.ts
index dc3d1e5b8e..3592b3d72b 100644
--- a/packages/backend-defaults/src/entrypoints/urlReader/lib/AwsS3UrlReader.test.ts
+++ b/packages/backend-defaults/src/entrypoints/urlReader/lib/AwsS3UrlReader.test.ts
@@ -128,6 +128,55 @@ describe('parseUrl', () => {
     });
   });
 
+  it('supports aws formats with custom endpoint hosts', () => {
+    expect(
+      parseUrl(
+        'https://bucket-1.s3.eu-central-1.amazonaws.com/path/to/file.yaml',
+        {
+          host: 'bucket-1.s3.eu-central-1.amazonaws.com',
+        },
+      ),
+    ).toEqual({
+      path: 'path/to/file.yaml',
+      bucket: 'bucket-1',
+      region: 'eu-central-1',
+    });
+    expect(
+      parseUrl('https://my-bucket.s3.cn-north-1.amazonaws.com.cn/data.json', {
+        host: 'my-bucket.s3.cn-north-1.amazonaws.com.cn',
+      }),
+    ).toEqual({
+      path: 'data.json',
+      bucket: 'my-bucket',
+      region: 'cn-north-1',
+    });
+    expect(
+      parseUrl(
+        'https://s3.eu-central-1.amazonaws.com/my-bucket/path/to/file.yaml',
+        {
+          host: 's3.eu-central-1.amazonaws.com',
+        },
+      ),
+    ).toEqual({
+      path: 'path/to/file.yaml',
+      bucket: 'my-bucket',
+      region: 'eu-central-1',
+    });
+    expect(
+      parseUrl(
+        'https://s3.eu-central-1.amazonaws.com/my-bucket/path/to/file.yaml',
+        {
+          host: 's3.eu-central-1.amazonaws.com',
+          s3ForcePathStyle: true,
+        },
+      ),
+    ).toEqual({
+      path: 'path/to/file.yaml',
+      bucket: 'my-bucket',
+      region: 'eu-central-1',
+    });
+  });
+
   it('supports all non-aws formats', () => {
     expect(
       parseUrl('https://my-host.com/my.bucket-3/a/puppy.jpg', {
diff --git a/packages/backend-defaults/src/entrypoints/urlReader/lib/AwsS3UrlReader.ts b/packages/backend-defaults/src/entrypoints/urlReader/lib/AwsS3UrlReader.ts
index cb776fc977..802397d526 100644
--- a/packages/backend-defaults/src/entrypoints/urlReader/lib/AwsS3UrlReader.ts
+++ b/packages/backend-defaults/src/entrypoints/urlReader/lib/AwsS3UrlReader.ts
@@ -74,7 +74,10 @@ export function parseUrl(
   const host = parsedUrl.host;
 
   // Treat Amazon hosted separately because it has special region logic
-  if (config.host === 'amazonaws.com' || config.host === 'amazonaws.com.cn') {
+  if (
+    config.host.endsWith('amazonaws.com') ||
+    config.host.endsWith('amazonaws.com.cn')
+  ) {
     const match = host.match(
       /^(?:([a-z0-9.-]+)\.)?s3(?:[.-]([a-z0-9-]+))?\.amazonaws\.com(\.cn)?$/,
     );