diff --git a/src/openrouter/sdk.py b/src/openrouter/sdk.py
index a6a9afda..83e8be0e 100644
--- a/src/openrouter/sdk.py
+++ b/src/openrouter/sdk.py
@@ -137,6 +137,7 @@ def __init__(
         server: Optional[str] = None,
         url_params: Optional[Dict[str, str]] = None,
         server_url: Optional[str] = None,
+        base_url: Optional[str] = None,
         client: Optional[HttpClient] = None,
         async_client: Optional[AsyncHttpClient] = None,
         retry_config: OptionalNullable[RetryConfig] = UNSET,
@@ -187,6 +188,9 @@ def __init__(
         else:
             security = components.Security(api_key=api_key)
 
+        if server_url is None and base_url is not None:
+            server_url = base_url
+
         if server_url is not None:
             if url_params is not None:
                 server_url = utils.template_url(server_url, url_params)
diff --git a/tests/test_sdk_base_url.py b/tests/test_sdk_base_url.py
new file mode 100644
index 00000000..7404be30
--- /dev/null
+++ b/tests/test_sdk_base_url.py
@@ -0,0 +1,11 @@
+import unittest
+from openrouter.sdk import OpenRouter
+
+class TestOpenRouterSDKBaseURL(unittest.TestCase):
+    def test_base_url_initialization(self):
+        custom_url = "https://custom.openrouter.ai/api/v1"
+        client = OpenRouter(api_key="test_key", base_url=custom_url)
+        self.assertEqual(client.sdk_configuration.server_url, custom_url)
+
+if __name__ == "__main__":
+    unittest.main()