diff --git a/google/genai/_api_client.py b/google/genai/_api_client.py
index 751211e51..5cb099735 100644
--- a/google/genai/_api_client.py
+++ b/google/genai/_api_client.py
@@ -552,6 +552,8 @@ def __del__(self) -> None:
 class BaseApiClient:
   """Client for calling HTTP APIs sending and receiving JSON."""
 
+  _VERTEXAI_MULTI_REGIONAL_LOCATIONS = ('us',)
+
   def __init__(
       self,
       vertexai: Optional[bool] = None,
@@ -686,6 +688,13 @@ def __init__(
           self.api_key or self.location == 'global'
       ) and not self.custom_base_url:
         self._http_options.base_url = f'https://aiplatform.googleapis.com/'
+      elif (
+          self.location in self._VERTEXAI_MULTI_REGIONAL_LOCATIONS
+          and not self.custom_base_url
+      ):
+        self._http_options.base_url = (
+            f'https://aiplatform.{self.location}.rep.googleapis.com/'
+        )
       elif (
           self.custom_base_url
           and not self.custom_base_url.endswith('.googleapis.com')
diff --git a/google/genai/tests/client/test_client_initialization.py b/google/genai/tests/client/test_client_initialization.py
index 7b0136044..b4c3a9811 100644
--- a/google/genai/tests/client/test_client_initialization.py
+++ b/google/genai/tests/client/test_client_initialization.py
@@ -515,6 +515,22 @@ def test_vertexai_no_default_location_when_location_explicitly_set(monkeypatch):
     assert client.models._api_client.project == project_id
 
 
+def test_vertexai_location_us_routing(monkeypatch):
+  # Verify that location='us' correctly routes to the us.rep endpoint
+  project_id = "fake_project_id"
+  location = "us"
+
+  with monkeypatch.context() as m:
+    m.delenv("GOOGLE_CLOUD_LOCATION", raising=False)
+    client = Client(vertexai=True, project=project_id, location=location)
+    assert client.models._api_client.location == location
+    assert client.models._api_client.project == project_id
+    assert (
+        client.models._api_client.get_read_only_http_options()["base_url"]
+        == "https://aiplatform.us.rep.googleapis.com/"
+    )
+
+
 def test_vertexai_no_default_location_when_env_location_set(monkeypatch):
   # Verify that location is NOT defaulted to global when set via environment
   project_id = "fake_project_id"