diff --git a/src/openai/_base_client.py b/src/openai/_base_client.py
index 7a8595c17..502ed7c7a 100644
--- a/src/openai/_base_client.py
+++ b/src/openai/_base_client.py
@@ -361,6 +361,11 @@ def __init__(
         self._strict_response_validation = _strict_response_validation
         self._idempotency_header = None
 
+        if max_retries is None:  # pyright: ignore[reportUnnecessaryComparison]
+            raise TypeError(
+                "max_retries cannot be None. If you want to disable retries, pass `0`; if you want unlimited retries, pass `math.inf` or a very high number; if you want the default behavior, pass `openai.DEFAULT_MAX_RETRIES`"
+            )
+
     def _enforce_trailing_slash(self, url: URL) -> URL:
         if url.raw_path.endswith(b"/"):
             return url
diff --git a/tests/test_client.py b/tests/test_client.py
index dab1cb0ef..ba85fd9d5 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -646,6 +646,10 @@ class Model(BaseModel):
 
         assert isinstance(exc.value.__cause__, ValidationError)
 
+    def test_client_max_retries_validation(self) -> None:
+        with pytest.raises(TypeError, match=r"max_retries cannot be None"):
+            OpenAI(base_url=base_url, api_key=api_key, _strict_response_validation=True, max_retries=cast(Any, None))
+
     @pytest.mark.respx(base_url=base_url)
     def test_default_stream_cls(self, respx_mock: MockRouter) -> None:
         class Model(BaseModel):
@@ -1368,6 +1372,12 @@ class Model(BaseModel):
 
         assert isinstance(exc.value.__cause__, ValidationError)
 
+    async def test_client_max_retries_validation(self) -> None:
+        with pytest.raises(TypeError, match=r"max_retries cannot be None"):
+            AsyncOpenAI(
+                base_url=base_url, api_key=api_key, _strict_response_validation=True, max_retries=cast(Any, None)
+            )
+
     @pytest.mark.respx(base_url=base_url)
     @pytest.mark.asyncio
     async def test_default_stream_cls(self, respx_mock: MockRouter) -> None: