diff --git a/pandas-stubs/core/frame.pyi b/pandas-stubs/core/frame.pyi
index c2efa8e31..37a2d13ca 100644
--- a/pandas-stubs/core/frame.pyi
+++ b/pandas-stubs/core/frame.pyi
@@ -785,7 +785,6 @@ class DataFrame(NDFrame, OpsMixin, _GetItemHack):
         *,
         axis: Axis | None = ...,
         limit: int = ...,
-        downcast: dict | None = ...,
         inplace: Literal[True],
     ) -> None: ...
     @overload
@@ -795,7 +794,6 @@ class DataFrame(NDFrame, OpsMixin, _GetItemHack):
         *,
         axis: Axis | None = ...,
         limit: int = ...,
-        downcast: dict | None = ...,
         inplace: Literal[False] = ...,
     ) -> Self: ...
     @overload
@@ -1719,7 +1717,6 @@ class DataFrame(NDFrame, OpsMixin, _GetItemHack):
         inplace: Literal[True],
         limit: int | None = ...,
         limit_area: Literal["inside", "outside"] | None = ...,
-        downcast: dict | None = ...,
     ) -> None: ...
     @overload
     def bfill(
@@ -1729,7 +1726,6 @@ class DataFrame(NDFrame, OpsMixin, _GetItemHack):
         inplace: Literal[False] = ...,
         limit: int | None = ...,
         limit_area: Literal["inside", "outside"] | None = ...,
-        downcast: dict | None = ...,
     ) -> Self: ...
     @overload
     def clip(
@@ -1812,7 +1808,6 @@ class DataFrame(NDFrame, OpsMixin, _GetItemHack):
         inplace: Literal[True],
         limit: int | None = ...,
         limit_area: Literal["inside", "outside"] | None = ...,
-        downcast: dict | None = ...,
     ) -> None: ...
     @overload
     def ffill(
@@ -1822,7 +1817,6 @@ class DataFrame(NDFrame, OpsMixin, _GetItemHack):
         inplace: Literal[False] = ...,
         limit: int | None = ...,
         limit_area: Literal["inside", "outside"] | None = ...,
-        downcast: dict | None = ...,
     ) -> Self: ...
     def filter(
         self,
@@ -1864,7 +1858,6 @@ class DataFrame(NDFrame, OpsMixin, _GetItemHack):
         limit: int | None = ...,
         limit_direction: Literal["forward", "backward", "both"] = ...,
         limit_area: Literal["inside", "outside"] | None = ...,
-        downcast: Literal["infer"] | None = ...,
         inplace: Literal[True],
         **kwargs,
     ) -> None: ...
@@ -1877,7 +1870,6 @@ class DataFrame(NDFrame, OpsMixin, _GetItemHack):
         limit: int | None = ...,
         limit_direction: Literal["forward", "backward", "both"] = ...,
         limit_area: Literal["inside", "outside"] | None = ...,
-        downcast: Literal["infer"] | None = ...,
         inplace: Literal[False] = ...,
         **kwargs,
     ) -> Self: ...
diff --git a/pandas-stubs/core/generic.pyi b/pandas-stubs/core/generic.pyi
index 7d3819ab5..2d6d5b667 100644
--- a/pandas-stubs/core/generic.pyi
+++ b/pandas-stubs/core/generic.pyi
@@ -437,26 +437,6 @@ class NDFrame(indexing.IndexingMixin):
         dtype_backend: DtypeBackend = ...,
     ) -> Self: ...
     @overload
-    def fillna(
-        self,
-        value=...,
-        *,
-        axis=...,
-        inplace: Literal[True],
-        limit=...,
-        downcast=...,
-    ) -> None: ...
-    @overload
-    def fillna(
-        self,
-        value=...,
-        *,
-        axis=...,
-        inplace: Literal[False] = ...,
-        limit=...,
-        downcast=...,
-    ) -> NDFrame: ...
-    @overload
     def replace(
         self,
         to_replace=...,
diff --git a/pandas-stubs/core/indexes/base.pyi b/pandas-stubs/core/indexes/base.pyi
index 88d29c218..5ebdcd224 100644
--- a/pandas-stubs/core/indexes/base.pyi
+++ b/pandas-stubs/core/indexes/base.pyi
@@ -321,7 +321,7 @@ class Index(IndexOpsMixin[S1]):
     isnull = ...
     def notna(self): ...
     notnull = ...
-    def fillna(self, value=..., downcast=...): ...
+    def fillna(self, value=...): ...
     def dropna(self, how: Literal["any", "all"] = ...) -> Self: ...
     def unique(self, level=...) -> Self: ...
     def drop_duplicates(self, *, keep: NaPosition | Literal[False] = ...) -> Self: ...
diff --git a/pandas-stubs/core/indexes/category.pyi b/pandas-stubs/core/indexes/category.pyi
index 18b3e1153..9740f52ea 100644
--- a/pandas-stubs/core/indexes/category.pyi
+++ b/pandas-stubs/core/indexes/category.pyi
@@ -35,7 +35,7 @@ class CategoricalIndex(ExtensionIndex[S1], accessor.PandasDelegate):
     def __contains__(self, key) -> bool: ...
     def __array__(self, dtype=...) -> np.ndarray: ...
     def astype(self, dtype: DtypeArg, copy: bool = ...) -> Index: ...
-    def fillna(self, value=..., downcast=...): ...
+    def fillna(self, value=...): ...
     @property
     def is_unique(self) -> bool: ...
     @property
diff --git a/pandas-stubs/core/indexes/multi.pyi b/pandas-stubs/core/indexes/multi.pyi
index 906df9bbe..13af9c68b 100644
--- a/pandas-stubs/core/indexes/multi.pyi
+++ b/pandas-stubs/core/indexes/multi.pyi
@@ -103,7 +103,6 @@ class MultiIndex(Index[Any]):
     @property
     def is_monotonic_decreasing(self) -> bool: ...
     def duplicated(self, keep: Literal["first", "last", False] = ...): ...
-    def fillna(self, value=..., downcast=...) -> None: ...
     def dropna(self, how: Literal["any", "all"] = ...) -> Self: ...
     def get_level_values(self, level: str | int) -> Index: ...
     def unique(self, level=...): ...
diff --git a/pandas-stubs/core/resample.pyi b/pandas-stubs/core/resample.pyi
index 2c4cc513f..6495a290a 100644
--- a/pandas-stubs/core/resample.pyi
+++ b/pandas-stubs/core/resample.pyi
@@ -27,7 +27,6 @@ from typing_extensions import (
     TypeAlias,
 )
 
-from pandas._libs.lib import NoDefault
 from pandas._typing import (
     S1,
     Axis,
@@ -105,7 +104,6 @@ class Resampler(BaseGroupBy[NDFrameT]):
         inplace: Literal[True],
         limit_direction: Literal["forward", "backward", "both"] = ...,
         limit_area: Literal["inside", "outside"] | None = ...,
-        downcast: Literal["infer"] | None | NoDefault = ...,
         **kwargs,
     ) -> None: ...
     @overload
@@ -118,7 +116,6 @@ class Resampler(BaseGroupBy[NDFrameT]):
         inplace: Literal[False] = ...,
         limit_direction: Literal["forward", "backward", "both"] = ...,
         limit_area: Literal["inside", "outside"] | None = ...,
-        downcast: Literal["infer"] | None | NoDefault = ...,
         **kwargs,
     ) -> NDFrameT: ...
     def asfreq(self, fill_value: Scalar | None = ...) -> NDFrameT: ...
diff --git a/pandas-stubs/core/series.pyi b/pandas-stubs/core/series.pyi
index 3a0a30991..ecf65ab51 100644
--- a/pandas-stubs/core/series.pyi
+++ b/pandas-stubs/core/series.pyi
@@ -1075,7 +1075,6 @@ class Series(IndexOpsMixin[S1], NDFrame):
         *,
         axis: AxisIndex = ...,
         limit: int | None = ...,
-        downcast: dict | None = ...,
         inplace: Literal[True],
     ) -> None: ...
     @overload
@@ -1085,7 +1084,6 @@ class Series(IndexOpsMixin[S1], NDFrame):
         *,
         axis: AxisIndex = ...,
         limit: int | None = ...,
-        downcast: dict | None = ...,
         inplace: Literal[False] = ...,
     ) -> Series[S1]: ...
     @overload
@@ -1302,7 +1300,6 @@ class Series(IndexOpsMixin[S1], NDFrame):
         inplace: Literal[True],
         limit: int | None = ...,
         limit_area: Literal["inside", "outside"] | None = ...,
-        downcast: dict | None = ...,
     ) -> None: ...
     @overload
     def ffill(
@@ -1312,7 +1309,6 @@ class Series(IndexOpsMixin[S1], NDFrame):
         inplace: Literal[False] = ...,
         limit: int | None = ...,
         limit_area: Literal["inside", "outside"] | None = ...,
-        downcast: dict | None = ...,
     ) -> Series[S1]: ...
     @overload
     def bfill(
@@ -1322,7 +1318,6 @@ class Series(IndexOpsMixin[S1], NDFrame):
         inplace: Literal[True],
         limit: int | None = ...,
         limit_area: Literal["inside", "outside"] | None = ...,
-        downcast: dict | None = ...,
     ) -> None: ...
     @overload
     def bfill(
@@ -1332,7 +1327,6 @@ class Series(IndexOpsMixin[S1], NDFrame):
         inplace: Literal[False] = ...,
         limit: int | None = ...,
         limit_area: Literal["inside", "outside"] | None = ...,
-        downcast: dict | None = ...,
     ) -> Series[S1]: ...
     @overload
     def interpolate(
@@ -1344,7 +1338,6 @@ class Series(IndexOpsMixin[S1], NDFrame):
         inplace: Literal[True],
         limit_direction: Literal["forward", "backward", "both"] | None = ...,
         limit_area: Literal["inside", "outside"] | None = ...,
-        downcast: Literal["infer"] | None = ...,
         **kwargs,
     ) -> None: ...
     @overload
@@ -1357,7 +1350,6 @@ class Series(IndexOpsMixin[S1], NDFrame):
         inplace: Literal[False] = ...,
         limit_direction: Literal["forward", "backward", "both"] | None = ...,
         limit_area: Literal["inside", "outside"] | None = ...,
-        downcast: Literal["infer"] | None = ...,
         **kwargs,
     ) -> Series[S1]: ...
     def asof(