diff --git a/narwhals/functions.py b/narwhals/functions.py
index 56457d3f31..b5f10927b6 100644
--- a/narwhals/functions.py
+++ b/narwhals/functions.py
@@ -9,8 +9,8 @@
 from typing import Literal
 from typing import Mapping
 from typing import Sequence
+from typing import TypeVar
 from typing import cast
-from typing import overload
 
 from narwhals._expression_parsing import ExpansionKind
 from narwhals._expression_parsing import ExprKind
@@ -57,46 +57,21 @@
     from narwhals.dtypes import DType
     from narwhals.schema import Schema
     from narwhals.series import Series
-    from narwhals.typing import IntoDataFrameT
     from narwhals.typing import IntoExpr
-    from narwhals.typing import IntoFrameT
     from narwhals.typing import IntoSeriesT
     from narwhals.typing import NativeFrame
     from narwhals.typing import NativeLazyFrame
     from narwhals.typing import _2DArray
 
     _IntoSchema: TypeAlias = "Mapping[str, DType] | Schema | Sequence[str] | None"
+    FrameT = TypeVar("FrameT", "DataFrame[Any]", "LazyFrame[Any]")
 
 
-@overload
 def concat(
-    items: Iterable[DataFrame[IntoDataFrameT]],
+    items: Iterable[FrameT],
     *,
     how: Literal["horizontal", "vertical", "diagonal"] = "vertical",
-) -> DataFrame[IntoDataFrameT]: ...
-
-
-@overload
-def concat(
-    items: Iterable[LazyFrame[IntoFrameT]],
-    *,
-    how: Literal["horizontal", "vertical", "diagonal"] = "vertical",
-) -> LazyFrame[IntoFrameT]: ...
-
-
-@overload
-def concat(
-    items: Iterable[DataFrame[IntoDataFrameT] | LazyFrame[IntoFrameT]],
-    *,
-    how: Literal["horizontal", "vertical", "diagonal"] = "vertical",
-) -> DataFrame[IntoDataFrameT] | LazyFrame[IntoFrameT]: ...
-
-
-def concat(
-    items: Iterable[DataFrame[IntoDataFrameT] | LazyFrame[IntoFrameT]],
-    *,
-    how: Literal["horizontal", "vertical", "diagonal"] = "vertical",
-) -> DataFrame[IntoDataFrameT] | LazyFrame[IntoFrameT]:
+) -> FrameT:
     """Concatenate multiple DataFrames, LazyFrames into a single entity.
 
     Arguments:
diff --git a/narwhals/stable/v1/__init__.py b/narwhals/stable/v1/__init__.py
index deb33e6481..79712278f4 100644
--- a/narwhals/stable/v1/__init__.py
+++ b/narwhals/stable/v1/__init__.py
@@ -99,6 +99,7 @@
     from narwhals.typing import _1DArray
     from narwhals.typing import _2DArray
 
+    FrameT = TypeVar("FrameT", "DataFrame[Any]", "LazyFrame[Any]")
     IntoSeriesT = TypeVar("IntoSeriesT", bound="IntoSeries", default=Any)
     T = TypeVar("T", default=Any)
 else:
@@ -2049,35 +2050,11 @@ def max_horizontal(*exprs: IntoExpr | Iterable[IntoExpr]) -> Expr:
     return _stableify(nw.max_horizontal(*exprs))
 
 
-@overload
-def concat(
-    items: Iterable[DataFrame[IntoDataFrameT]],
-    *,
-    how: Literal["horizontal", "vertical", "diagonal"] = "vertical",
-) -> DataFrame[IntoDataFrameT]: ...
-
-
-@overload
-def concat(
-    items: Iterable[LazyFrame[IntoFrameT]],
-    *,
-    how: Literal["horizontal", "vertical", "diagonal"] = "vertical",
-) -> LazyFrame[IntoFrameT]: ...
-
-
-@overload
-def concat(
-    items: Iterable[DataFrame[IntoDataFrameT] | LazyFrame[IntoFrameT]],
-    *,
-    how: Literal["horizontal", "vertical", "diagonal"] = "vertical",
-) -> DataFrame[IntoDataFrameT] | LazyFrame[IntoFrameT]: ...
-
-
 def concat(
-    items: Iterable[DataFrame[IntoDataFrameT] | LazyFrame[IntoFrameT]],
+    items: Iterable[FrameT],
     *,
     how: Literal["horizontal", "vertical", "diagonal"] = "vertical",
-) -> DataFrame[IntoDataFrameT] | LazyFrame[IntoFrameT]:
+) -> FrameT:
     """Concatenate multiple DataFrames, LazyFrames into a single entity.
 
     Arguments:
@@ -2096,7 +2073,7 @@ def concat(
     Raises:
         TypeError: The items to concatenate should either all be eager, or all lazy
     """
-    return _stableify(nw.concat(items, how=how))
+    return cast("FrameT", _stableify(nw.concat(items, how=how)))
 
 
 def concat_str(
diff --git a/tests/frame/invalid_test.py b/tests/frame/invalid_test.py
index 0891d55adc..888a4c0010 100644
--- a/tests/frame/invalid_test.py
+++ b/tests/frame/invalid_test.py
@@ -83,7 +83,7 @@ def test_validate_laziness() -> None:
         TypeError,
         match=("The items to concatenate should either all be eager, or all lazy"),
     ):
-        nw.concat([nw.from_native(df, eager_only=True), nw.from_native(df).lazy()])
+        nw.concat([nw.from_native(df, eager_only=True), nw.from_native(df).lazy()])  # type: ignore[type-var]
 
 
 @pytest.mark.slow