diff --git a/litellm/llms/bedrock/common_utils.py b/litellm/llms/bedrock/common_utils.py
index 66ee5f10679..1e5329c90dd 100644
--- a/litellm/llms/bedrock/common_utils.py
+++ b/litellm/llms/bedrock/common_utils.py
@@ -748,6 +748,15 @@ def strip_bedrock_throughput_suffix(model: str) -> str:
 
 
 MANTLE_MESSAGES_PATH: Final = "/anthropic/v1/messages"
+_MANTLE_OPENAI_BASE_SUFFIXES: Final = ("/openai/v1", "/v1")
+
+
+def _mantle_api_base_from_env() -> str | None:
+    env_base: Final = get_secret_str("BEDROCK_MANTLE_API_BASE")
+    if env_base is None:
+        return None
+    base: Final = env_base.rstrip("/")
+    return next((base[: -len(suffix)] for suffix in _MANTLE_OPENAI_BASE_SUFFIXES if base.endswith(suffix)), base)
 
 
 def build_mantle_messages_url(
@@ -758,12 +767,15 @@ def build_mantle_messages_url(
     """Build the bedrock-mantle Anthropic /messages URL.
 
     Honors an explicit endpoint override (``api_base``, then
-    ``aws_bedrock_runtime_endpoint``) so private VPC / VPCE / GovCloud Mantle
-    endpoints are reachable; otherwise falls back to the public regional host.
+    ``aws_bedrock_runtime_endpoint``, then ``BEDROCK_MANTLE_API_BASE``) so
+    private VPC / VPCE / GovCloud Mantle endpoints are reachable; otherwise
+    falls back to the public regional host.
     The mantle messages path is appended unless the override already carries it,
-    so callers can pass either the host or the full messages URL.
+    so callers can pass either the host or the full messages URL. The env var is
+    shared with the OpenAI-surface ``bedrock_mantle/*`` routes, which need it to
+    carry their ``/v1`` or ``/openai/v1`` base, so that suffix is dropped first.
     """
-    override: Final = api_base or aws_bedrock_runtime_endpoint
+    override: Final = api_base or aws_bedrock_runtime_endpoint or _mantle_api_base_from_env()
     if override:
         base: Final = override.rstrip("/")
         if base.endswith(MANTLE_MESSAGES_PATH):
diff --git a/tests/test_litellm/llms/bedrock/test_mantle.py b/tests/test_litellm/llms/bedrock/test_mantle.py
index d34517f61f6..09be2118001 100644
--- a/tests/test_litellm/llms/bedrock/test_mantle.py
+++ b/tests/test_litellm/llms/bedrock/test_mantle.py
@@ -128,6 +128,12 @@ def test_mantle_messages_url_construction():
 _VPC_ENDPOINT = "https://vpce-0a1b2c3d.bedrock-mantle.us-gov-west-1.vpce.amazonaws.com"
 
 
+@pytest.fixture(autouse=True)
+def no_ambient_mantle_api_base(monkeypatch):
+    monkeypatch.delenv("BEDROCK_MANTLE_API_BASE", raising=False)
+
+
+
 def test_mantle_chat_url_honors_api_base_host():
     config = AmazonMantleConfig()
     url = config.get_complete_url(
@@ -193,6 +199,48 @@ def test_mantle_messages_url_honors_aws_bedrock_runtime_endpoint():
     assert url == f"{_VPC_ENDPOINT}/anthropic/v1/messages"
 
 
+_ENV_ENDPOINT = "https://bedrock-mantle.us-east-1.api.aws.internal.example.com"
+
+
+@pytest.mark.parametrize("config_cls", [AmazonMantleConfig, AmazonMantleMessagesConfig])
+@pytest.mark.parametrize(
+    "env_value",
+    [_ENV_ENDPOINT, f"{_ENV_ENDPOINT}/", f"{_ENV_ENDPOINT}/v1", f"{_ENV_ENDPOINT}/openai/v1"],
+)
+def test_mantle_url_honors_bedrock_mantle_api_base_env(monkeypatch, config_cls, env_value):
+    monkeypatch.setenv("BEDROCK_MANTLE_API_BASE", env_value)
+    url = config_cls().get_complete_url(
+        api_base=None,
+        api_key=None,
+        model="mantle/anthropic.claude-mythos-preview",
+        optional_params={"aws_region_name": "us-east-1"},
+        litellm_params={},
+    )
+    assert url == f"{_ENV_ENDPOINT}/anthropic/v1/messages"
+
+
+@pytest.mark.parametrize("config_cls", [AmazonMantleConfig, AmazonMantleMessagesConfig])
+@pytest.mark.parametrize(
+    ("api_base", "optional_params"),
+    [
+        (_VPC_ENDPOINT, {"aws_region_name": "us-gov-west-1"}),
+        (None, {"aws_region_name": "us-gov-west-1", "aws_bedrock_runtime_endpoint": _VPC_ENDPOINT}),
+    ],
+)
+def test_mantle_url_explicit_endpoint_beats_bedrock_mantle_api_base_env(
+    monkeypatch, config_cls, api_base, optional_params
+):
+    monkeypatch.setenv("BEDROCK_MANTLE_API_BASE", _ENV_ENDPOINT)
+    url = config_cls().get_complete_url(
+        api_base=api_base,
+        api_key=None,
+        model="mantle/anthropic.claude-mythos-preview",
+        optional_params=optional_params,
+        litellm_params={},
+    )
+    assert url == f"{_VPC_ENDPOINT}/anthropic/v1/messages"
+
+
 def test_mantle_transform_request_strips_prefix_and_adds_model():
     config = AmazonMantleConfig()
     request = config.transform_request(