diff --git a/spec/API_specification/dataframe_api/dataframe_object.py b/spec/API_specification/dataframe_api/dataframe_object.py
index 7de9d006..abb0fbe8 100644
--- a/spec/API_specification/dataframe_api/dataframe_object.py
+++ b/spec/API_specification/dataframe_api/dataframe_object.py
@@ -1,5 +1,5 @@
 from __future__ import annotations
-from typing import Sequence, Union, TYPE_CHECKING
+from typing import Sequence, Union, TYPE_CHECKING, NoReturn
 
 if TYPE_CHECKING:
     from .column_object import Column
@@ -418,6 +418,18 @@ def __divmod__(self, other: DataFrame | Scalar) -> tuple[DataFrame, DataFrame]:
         """
         ...
 
+    def __iter__(self) -> NoReturn:
+        """
+        Iterate over elements.
+
+        This is intentionally "poisoned" to discourage inefficient code patterns.
+
+        Raises
+        ------
+        NotImplementedError
+        """
+        raise NotImplementedError("'__iter__' is intentionally not implemented.")
+
     def any(self, skipna: bool = True) -> DataFrame:
         """
         Reduction returns a 1-row DataFrame.