diff --git a/litellm/litellm_core_utils/get_llm_provider_logic.py b/litellm/litellm_core_utils/get_llm_provider_logic.py
index 864405749f7..f7fa7fe40a7 100644
--- a/litellm/litellm_core_utils/get_llm_provider_logic.py
+++ b/litellm/litellm_core_utils/get_llm_provider_logic.py
@@ -159,6 +159,14 @@ def get_llm_provider(  # noqa: PLR0915
         ):  # handle scenario where model="azure/*" and custom_llm_provider="azure"
             model = custom_llm_provider + "/" + model
 
+        # Native OpenRouter models have IDs like "openrouter/free" where the
+        # "openrouter/" prefix is part of the actual model name on the API.
+        # When called from a bridge (e.g. anthropic_messages adapter),
+        # custom_llm_provider is already resolved, so return early to prevent
+        # the provider-list stripping below from removing the prefix.
+        if custom_llm_provider == "openrouter" and model.startswith("openrouter/"):
+            return model, custom_llm_provider, dynamic_api_key, api_base
+
         if api_key and api_key.startswith("os.environ/"):
             dynamic_api_key = get_secret_str(api_key)
 
diff --git a/tests/test_litellm/llms/openrouter/test_openrouter_provider_routing.py b/tests/test_litellm/llms/openrouter/test_openrouter_provider_routing.py
new file mode 100644
index 00000000000..72cf2eec371
--- /dev/null
+++ b/tests/test_litellm/llms/openrouter/test_openrouter_provider_routing.py
@@ -0,0 +1,90 @@
+"""
+Tests for OpenRouter model name routing in get_llm_provider.
+
+OpenRouter-native models have IDs that start with "openrouter/" (e.g.
+openrouter/auto, openrouter/free, openrouter/aurora-alpha).  When a user
+configures such a model in LiteLLM they use the double-prefixed form
+"openrouter/openrouter/aurora-alpha".  get_llm_provider must strip only
+the outer "openrouter/" provider prefix and leave the inner one intact,
+so the correct model ID is sent to the OpenRouter API.
+
+See: https://github.com/BerriAI/litellm/issues/16353
+"""
+
+import os
+import sys
+
+import pytest
+
+sys.path.insert(0, os.path.abspath("../../../../.."))
+
+import litellm
+
+
+class TestOpenRouterNativeModelRouting:
+    """get_llm_provider must not double-strip native OpenRouter model names."""
+
+    @pytest.mark.parametrize(
+        "input_model,expected_model",
+        [
+            # Well-known native models
+            ("openrouter/openrouter/auto", "openrouter/auto"),
+            ("openrouter/openrouter/free", "openrouter/free"),
+            ("openrouter/openrouter/bodybuilder", "openrouter/bodybuilder"),
+            # Arbitrary native models — the fix must be pattern-based, not a hardcoded list
+            ("openrouter/openrouter/aurora-alpha", "openrouter/aurora-alpha"),
+            ("openrouter/openrouter/polaris-alpha", "openrouter/polaris-alpha"),
+            ("openrouter/openrouter/some-future-model", "openrouter/some-future-model"),
+        ],
+    )
+    def test_double_prefixed_strips_once(self, input_model, expected_model):
+        """openrouter/openrouter/<model> should yield model=openrouter/<model>."""
+        result_model, provider, _, _ = litellm.get_llm_provider(model=input_model)
+        assert provider == "openrouter"
+        assert result_model == expected_model
+
+    @pytest.mark.parametrize(
+        "input_model",
+        [
+            "openrouter/openrouter/aurora-alpha",
+            "openrouter/openrouter/auto",
+            "openrouter/openrouter/free",
+            "openrouter/openrouter/some-future-model",
+        ],
+    )
+    def test_bridge_double_call_preserves_native_model(self, input_model):
+        """Simulates two consecutive get_llm_provider calls (bridge → completion).
+
+        The first call (bridge) strips the outer prefix:
+            openrouter/openrouter/<model> → openrouter/<model>
+
+        The second call (completion) receives custom_llm_provider="openrouter"
+        from the bridge, detects the native model, and preserves it:
+            openrouter/<model> → openrouter/<model>  (no further stripping)
+        """
+        # First call: bridge resolves provider
+        model_first, provider, _, _ = litellm.get_llm_provider(model=input_model)
+        assert provider == "openrouter"
+        expected_model = input_model.split("/", 1)[1]  # openrouter/<model>
+        assert model_first == expected_model
+
+        # Second call: completion receives model + custom_llm_provider from bridge
+        model_second, provider2, _, _ = litellm.get_llm_provider(
+            model=model_first,
+            custom_llm_provider="openrouter",
+        )
+        assert provider2 == "openrouter"
+        assert model_second == expected_model  # preserved, not stripped further
+
+    @pytest.mark.parametrize(
+        "input_model,expected_model",
+        [
+            ("openrouter/anthropic/claude-3-haiku", "anthropic/claude-3-haiku"),
+            ("openrouter/meta-llama/llama-3-70b-instruct", "meta-llama/llama-3-70b-instruct"),
+        ],
+    )
+    def test_regular_models_still_strip_normally(self, input_model, expected_model):
+        """Non-native OpenRouter models should still have their prefix stripped."""
+        result_model, provider, _, _ = litellm.get_llm_provider(model=input_model)
+        assert provider == "openrouter"
+        assert result_model == expected_model