diff --git a/litellm/llms/azure/responses/transformation.py b/litellm/llms/azure/responses/transformation.py
index 6a0740b2f15..74ca5a38d8a 100644
--- a/litellm/llms/azure/responses/transformation.py
+++ b/litellm/llms/azure/responses/transformation.py
@@ -137,7 +137,13 @@ class AzureOpenAIResponsesAPIConfig(OpenAIResponsesAPIConfig):
         return BaseAzureLLM.base_validate_azure_environment(headers=headers, litellm_params=litellm_params)
 
     def get_stripped_model_name(self, model: str) -> str:
-        return model.replace("responses/", "").replace("o_series/", "").replace("azure_ai/", "")
+        # gpt5_series/ is a litellm routing marker, not part of the Azure deployment name
+        return (
+            model.replace("responses/", "")
+            .replace("o_series/", "")
+            .replace("azure_ai/", "")
+            .replace(AzureOpenAIGPT5Config.GPT5_SERIES_ROUTE, "")
+        )
 
     def _validate_input_param(
         self, input: str | ResponseInputParam, *, drop_params: bool = False
diff --git a/tests/unit/llms/azure/response/test_azure_transformation.py b/tests/unit/llms/azure/response/test_azure_transformation.py
index 05c0817e19b..1e70ed2e1b3 100644
--- a/tests/unit/llms/azure/response/test_azure_transformation.py
+++ b/tests/unit/llms/azure/response/test_azure_transformation.py
@@ -27,6 +27,30 @@ from litellm.utils import ProviderConfigManager
 from tests.unit.proxy.conftest import httpx_transport
 
 
+@pytest.mark.serial
+def test_get_stripped_model_name_strips_gpt5_series_route():
+    """The gpt5_series/ routing marker must not be sent to Azure as part of the deployment name."""
+    config = AzureOpenAIResponsesAPIConfig()
+
+    assert (
+        config.get_stripped_model_name("azure/gpt5_series/my-gpt5-deployment")
+        == "azure/my-gpt5-deployment"
+    )
+    assert (
+        config.get_stripped_model_name("azure/responses/gpt5_series/my-gpt5-deployment")
+        == "azure/my-gpt5-deployment"
+    )
+    # existing markers still strip, and plain deployments pass through untouched
+    assert (
+        config.get_stripped_model_name("azure/o_series/my-o3-deployment")
+        == "azure/my-o3-deployment"
+    )
+    assert (
+        config.get_stripped_model_name("azure/my-gpt5-deployment")
+        == "azure/my-gpt5-deployment"
+    )
+
+
 @pytest.mark.serial
 def test_validate_environment_api_key_within_litellm_params():
     azure_openai_responses_apiconfig = AzureOpenAIResponsesAPIConfig()