diff --git a/pandas/core/base.py b/pandas/core/base.py
index a1484d9ad032b..cb8848db9af60 100644
--- a/pandas/core/base.py
+++ b/pandas/core/base.py
@@ -218,7 +218,7 @@ def _obj_with_exclusions(self):
             return self.obj
 
         if self._selection is not None:
-            return self.obj._getitem_nocopy(self._selection_list)
+            return self.obj[self._selection_list]
 
         if len(self.exclusions) > 0:
             # equivalent to `self.obj.drop(self.exclusions, axis=1)
diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index 771554f2b0f2b..85e13401d6e32 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -1676,8 +1676,8 @@ def dot(self, other: AnyArrayLike | DataFrame) -> DataFrame | Series:
             if len(common) > len(self.columns) or len(common) > len(other.index):
                 raise ValueError("matrices are not aligned")
 
-            left = self.reindex(columns=common, copy=False)
-            right = other.reindex(index=common, copy=False)
+            left = self.reindex(columns=common)
+            right = other.reindex(index=common)
             lvals = left.values
             rvals = right._values
         else:
@@ -3800,27 +3800,6 @@ def _iter_column_arrays(self) -> Iterator[ArrayLike]:
         for i in range(len(self.columns)):
             yield self._get_column_array(i)
 
-    def _getitem_nocopy(self, key: list):
-        """
-        Behaves like __getitem__, but returns a view in cases where __getitem__
-        would make a copy.
-        """
-        # TODO(CoW): can be removed if/when we are always Copy-on-Write
-        indexer = self.columns._get_indexer_strict(key, "columns")[1]
-        new_axis = self.columns[indexer]
-
-        new_mgr = self._mgr.reindex_indexer(
-            new_axis,
-            indexer,
-            axis=0,
-            allow_dups=True,
-            copy=False,
-            only_slice=True,
-        )
-        result = self._constructor_from_mgr(new_mgr, axes=new_mgr.axes)
-        result = result.__finalize__(self)
-        return result
-
     def __getitem__(self, key):
         check_dict_or_set_indexers(key)
         key = lib.item_from_zerodim(key)
@@ -3911,7 +3890,7 @@ def _getitem_bool_array(self, key):
         key = check_bool_indexer(self.index, key)
 
         if key.all():
-            return self.copy(deep=None)
+            return self.copy(deep=False)
 
         indexer = key.nonzero()[0]
         return self.take(indexer, axis=0)
@@ -4774,7 +4753,7 @@ def predicate(arr: ArrayLike) -> bool:
 
             return True
 
-        mgr = self._mgr._get_data_subset(predicate).copy(deep=None)
+        mgr = self._mgr._get_data_subset(predicate).copy(deep=False)
         return self._constructor_from_mgr(mgr, axes=mgr.axes).__finalize__(self)
 
     def insert(
@@ -4919,7 +4898,7 @@ def assign(self, **kwargs) -> DataFrame:
         Portland    17.0    62.6  290.15
         Berkeley    25.0    77.0  298.15
         """
-        data = self.copy(deep=None)
+        data = self.copy(deep=False)
 
         for k, v in kwargs.items():
             data[k] = com.apply_if_callable(v, data)
@@ -4996,7 +4975,6 @@ def _reindex_multi(self, axes: dict[str, Index], fill_value) -> DataFrame:
         else:
             return self._reindex_with_indexers(
                 {0: [new_index, row_indexer], 1: [new_columns, col_indexer]},
-                copy=False,
                 fill_value=fill_value,
             )
 
@@ -5038,7 +5016,7 @@ def set_axis(
         axis: Axis = 0,
         copy: bool | None = None,
     ) -> DataFrame:
-        return super().set_axis(labels, axis=axis, copy=copy)
+        return super().set_axis(labels, axis=axis)
 
     @doc(
         NDFrame.reindex,
@@ -5065,7 +5043,6 @@ def reindex(
             columns=columns,
             axis=axis,
             method=method,
-            copy=copy,
             level=level,
             fill_value=fill_value,
             limit=limit,
@@ -5463,7 +5440,6 @@ def rename(
             index=index,
             columns=columns,
             axis=axis,
-            copy=copy,
             inplace=inplace,
             level=level,
             errors=errors,
@@ -5534,7 +5510,7 @@ def _replace_columnwise(
         DataFrame or None
         """
         # Operate column-wise
-        res = self if inplace else self.copy(deep=None)
+        res = self if inplace else self.copy(deep=False)
         ax = self.columns
 
         for i, ax_value in enumerate(ax):
@@ -5823,8 +5799,7 @@ def set_index(
         if inplace:
             frame = self
         else:
-            # GH 49473 Use "lazy copy" with Copy-on-Write
-            frame = self.copy(deep=None)
+            frame = self.copy(deep=False)
 
         arrays: list[Index] = []
         names: list[Hashable] = []
@@ -6114,7 +6089,7 @@ class    max    type
         if inplace:
             new_obj = self
         else:
-            new_obj = self.copy(deep=None)
+            new_obj = self.copy(deep=False)
         if allow_duplicates is not lib.no_default:
             allow_duplicates = validate_bool_kwarg(allow_duplicates, "allow_duplicates")
 
@@ -6386,7 +6361,7 @@ def dropna(
             raise ValueError(f"invalid how option: {how}")
 
         if np.all(mask):
-            result = self.copy(deep=None)
+            result = self.copy(deep=False)
         else:
             result = self.loc(axis=axis)[mask]
 
@@ -6515,7 +6490,7 @@ def drop_duplicates(
         4  Indomie  pack     5.0
         """
         if self.empty:
-            return self.copy(deep=None)
+            return self.copy(deep=False)
 
         inplace = validate_bool_kwarg(inplace, "inplace")
         ignore_index = validate_bool_kwarg(ignore_index, "ignore_index")
@@ -6631,7 +6606,7 @@ def duplicated(
 
         def f(vals) -> tuple[np.ndarray, int]:
             labels, shape = algorithms.factorize(vals, size_hint=len(self))
-            return labels.astype("i8", copy=False), len(shape)
+            return labels.astype("i8"), len(shape)
 
         if subset is None:
             # https://github.com/pandas-dev/pandas/issues/28770
@@ -6914,7 +6889,7 @@ def sort_values(
             if inplace:
                 return self._update_inplace(self)
             else:
-                return self.copy(deep=None)
+                return self.copy(deep=False)
 
         if is_range_indexer(indexer, len(indexer)):
             result = self.copy(deep=False)
@@ -7570,7 +7545,7 @@ def nsmallest(
         ),
     )
     def swaplevel(self, i: Axis = -2, j: Axis = -1, axis: Axis = 0) -> DataFrame:
-        result = self.copy(deep=None)
+        result = self.copy(deep=False)
 
         axis = self._get_axis_number(axis)
 
@@ -7630,7 +7605,7 @@ class      diet
         if not isinstance(self._get_axis(axis), MultiIndex):  # pragma: no cover
             raise TypeError("Can only reorder levels on a hierarchical axis.")
 
-        result = self.copy(deep=None)
+        result = self.copy(deep=False)
 
         if axis == 0:
             assert isinstance(result.index, MultiIndex)
@@ -7933,9 +7908,7 @@ def to_series(right):
         if flex is not None and isinstance(right, DataFrame):
             if not left._indexed_same(right):
                 if flex:
-                    left, right = left.align(
-                        right, join="outer", level=level, copy=False
-                    )
+                    left, right = left.align(right, join="outer", level=level)
                 else:
                     raise ValueError(
                         "Can only compare identically-labeled (both index and columns) "
@@ -7948,7 +7921,7 @@ def to_series(right):
                 if not left.axes[axis].equals(right.index):
                     raise ValueError(
                         "Operands are not aligned. Do "
-                        "`left, right = left.align(right, axis=1, copy=False)` "
+                        "`left, right = left.align(right, axis=1)` "
                         "before operating."
                     )
 
@@ -7957,7 +7930,6 @@ def to_series(right):
                 join="outer",
                 axis=axis,
                 level=level,
-                copy=False,
             )
             right = left._maybe_align_series_as_frame(right, axis)
 
@@ -8467,7 +8439,7 @@ def combine(
         """
         other_idxlen = len(other.index)  # save for compare
 
-        this, other = self.align(other, copy=False)
+        this, other = self.align(other)
         new_index = this.index
 
         if other.empty and len(new_index) == len(self.index):
@@ -8507,15 +8479,15 @@ def combine(
                 # try to promote series, which is all NaN, as other_dtype.
                 new_dtype = other_dtype
                 try:
-                    series = series.astype(new_dtype, copy=False)
+                    series = series.astype(new_dtype)
                 except ValueError:
                     # e.g. new_dtype is integer types
                     pass
             else:
                 # if we have different dtypes, possibly promote
                 new_dtype = find_common_type([this_dtype, other_dtype])
-                series = series.astype(new_dtype, copy=False)
-                other_series = other_series.astype(new_dtype, copy=False)
+                series = series.astype(new_dtype)
+                other_series = other_series.astype(new_dtype)
 
             arr = func(series, other_series)
             if isinstance(new_dtype, np.dtype):
@@ -9567,7 +9539,7 @@ def explode(
             result.index = default_index(len(result))
         else:
             result.index = self.index.take(result.index)
-        result = result.reindex(columns=self.columns, copy=False)
+        result = result.reindex(columns=self.columns)
 
         return result.__finalize__(self, method="explode")
 
@@ -10263,9 +10235,7 @@ def _append(
             row_df = other.to_frame().T
             # infer_objects is needed for
             #  test_append_empty_frame_to_series_with_dateutil_tz
-            other = row_df.infer_objects(copy=False).rename_axis(
-                index.names, copy=False
-            )
+            other = row_df.infer_objects().rename_axis(index.names)
         elif isinstance(other, list):
             if not other:
                 pass
@@ -10509,7 +10479,7 @@ def join(
                     res = concat(
                         frames, axis=1, join="outer", verify_integrity=True, sort=sort
                     )
-                    return res.reindex(self.index, copy=False)
+                    return res.reindex(self.index)
                 else:
                     return concat(
                         frames, axis=1, join=how, verify_integrity=True, sort=sort
@@ -10559,7 +10529,6 @@ def merge(
             right_index=right_index,
             sort=sort,
             suffixes=suffixes,
-            copy=copy,
             indicator=indicator,
             validate=validate,
         )
@@ -11024,7 +10993,7 @@ def corrwith(
 
         if numeric_only:
             other = other._get_numeric_data()
-        left, right = this.align(other, join="inner", copy=False)
+        left, right = this.align(other, join="inner")
 
         if axis == 1:
             left = left.T
@@ -11161,7 +11130,7 @@ def count(self, axis: Axis = 0, numeric_only: bool = False):
         else:
             result = notna(frame).sum(axis=axis)
 
-        return result.astype("int64", copy=False).__finalize__(self, method="count")
+        return result.astype("int64").__finalize__(self, method="count")
 
     def _reduce(
         self,
@@ -11225,7 +11194,7 @@ def _get_data() -> DataFrame:
         if axis is None:
             dtype = find_common_type([arr.dtype for arr in df._mgr.arrays])
             if isinstance(dtype, ExtensionDtype):
-                df = df.astype(dtype, copy=False)
+                df = df.astype(dtype)
                 arr = concat_compat(list(df._iter_column_arrays()))
                 return arr._reduce(name, skipna=skipna, keepdims=False, **kwds)
             return func(df.values)
@@ -11257,7 +11226,7 @@ def _get_data() -> DataFrame:
                     # be equivalent to transposing the original frame and aggregating
                     # with axis=0.
                     name = {"argmax": "idxmax", "argmin": "idxmin"}.get(name, name)
-                    df = df.astype(dtype, copy=False)
+                    df = df.astype(dtype)
                     arr = concat_compat(list(df._iter_column_arrays()))
                     nrows, ncols = df.shape
                     row_index = np.tile(np.arange(nrows), ncols)
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 3502754eb4aff..8e0767d9b3699 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -735,15 +735,13 @@ def set_axis(
         --------
         %(klass)s.rename_axis : Alter the name of the index%(see_also_sub)s.
         """
-        return self._set_axis_nocheck(labels, axis, inplace=False, copy=copy)
+        return self._set_axis_nocheck(labels, axis, inplace=False)
 
     @final
-    def _set_axis_nocheck(self, labels, axis: Axis, inplace: bool, copy: bool | None):
+    def _set_axis_nocheck(self, labels, axis: Axis, inplace: bool):
         if inplace:
             setattr(self, self._get_axis_name(axis), labels)
         else:
-            # With copy=False, we create a new object but don't copy the
-            #  underlying data.
             obj = self.copy(deep=False)
             setattr(obj, obj._get_axis_name(axis), labels)
             return obj
@@ -880,7 +878,7 @@ def droplevel(self, level: IndexLabel, axis: Axis = 0) -> Self:
         """
         labels = self._get_axis(axis)
         new_labels = labels.droplevel(level)
-        return self.set_axis(new_labels, axis=axis, copy=None)
+        return self.set_axis(new_labels, axis=axis)
 
     def pop(self, item: Hashable) -> Series | Any:
         result = self[item]
@@ -1069,7 +1067,7 @@ def _rename(
                     raise KeyError(f"{missing_labels} not found in axis")
 
             new_index = ax._transform_index(f, level=level)
-            result._set_axis_nocheck(new_index, axis=axis_no, inplace=True, copy=False)
+            result._set_axis_nocheck(new_index, axis=axis_no, inplace=True)
 
         if inplace:
             self._update_inplace(result)
@@ -4137,9 +4135,7 @@ def _getitem_slice(self, key: slice) -> Self:
         slobj = self.index._convert_slice_indexer(key, kind="getitem")
         if isinstance(slobj, np.ndarray):
             # reachable with DatetimeIndex
-            indexer = lib.maybe_indices_to_slice(
-                slobj.astype(np.intp, copy=False), len(self)
-            )
+            indexer = lib.maybe_indices_to_slice(slobj.astype(np.intp), len(self))
             if isinstance(indexer, np.ndarray):
                 # GH#43223 If we can not convert, use take
                 return self.take(indexer, axis=0)
@@ -4385,7 +4381,6 @@ def reindex_like(
         d = other._construct_axes_dict(
             axes=self._AXIS_ORDERS,
             method=method,
-            copy=copy,
             limit=limit,
             tolerance=tolerance,
         )
@@ -4551,7 +4546,6 @@ def _drop_axis(
             indexer,
             axis=bm_axis,
             allow_dups=True,
-            copy=None,
             only_slice=only_slice,
         )
         result = self._constructor_from_mgr(new_mgr, axes=new_mgr.axes)
@@ -4992,7 +4986,7 @@ def sort_index(
             if inplace:
                 result = self
             else:
-                result = self.copy(deep=None)
+                result = self.copy(deep=False)
 
             if ignore_index:
                 if axis == 1:
@@ -5290,7 +5284,7 @@ def reindex(
 
         # perform the reindex on the axes
         return self._reindex_axes(
-            axes, level, limit, tolerance, method, fill_value, False
+            axes, level, limit, tolerance, method, fill_value
         ).__finalize__(self, method="reindex")
 
     @final
@@ -5302,7 +5296,6 @@ def _reindex_axes(
         tolerance,
         method,
         fill_value: Scalar | None,
-        copy: bool | None,
     ) -> Self:
         """Perform the reindex for all the axes."""
         obj = self
@@ -5320,11 +5313,8 @@ def _reindex_axes(
             obj = obj._reindex_with_indexers(
                 {axis: [new_index, indexer]},
                 fill_value=fill_value,
-                copy=copy,
                 allow_dups=False,
             )
-            # If we've made a copy once, no need to make another one
-            copy = False
 
         return obj
 
@@ -5347,7 +5337,6 @@ def _reindex_with_indexers(
         self,
         reindexers,
         fill_value=None,
-        copy: bool | None = False,
         allow_dups: bool = False,
     ) -> Self:
         """allow_dups indicates an internal call here"""
@@ -5371,10 +5360,7 @@ def _reindex_with_indexers(
                 axis=baxis,
                 fill_value=fill_value,
                 allow_dups=allow_dups,
-                copy=copy,
             )
-            # If we've made a copy once, no need to make another one
-            copy = False
 
         if new_data is self._mgr:
             new_data = new_data.copy(deep=False)
@@ -6307,7 +6293,7 @@ def astype(
                         f"'{col_name}' not found in columns."
                     )
 
-            dtype_ser = dtype_ser.reindex(self.columns, fill_value=None, copy=False)
+            dtype_ser = dtype_ser.reindex(self.columns, fill_value=None)
 
             results = []
             for i, (col_name, col) in enumerate(self.items()):
@@ -7000,11 +6986,11 @@ def fillna(
                         # test_fillna_nonscalar
                         if inplace:
                             return None
-                        return self.copy(deep=None)
+                        return self.copy(deep=False)
                     from pandas import Series
 
                     value = Series(value)
-                    value = value.reindex(self.index, copy=False)
+                    value = value.reindex(self.index)
                     value = value._values
                 elif not is_list_like(value):
                     pass
@@ -9820,7 +9806,6 @@ def align(
                     join=join,
                     axis=axis,
                     level=level,
-                    copy=copy,
                     fill_value=fill_value,
                     method=method,
                     limit=limit,
@@ -9840,7 +9825,6 @@ def align(
                     join=join,
                     axis=axis,
                     level=level,
-                    copy=copy,
                     fill_value=fill_value,
                     method=method,
                     limit=limit,
@@ -9856,7 +9840,6 @@ def align(
                 join=join,
                 axis=axis,
                 level=level,
-                copy=copy,
                 fill_value=fill_value,
                 method=method,
                 limit=limit,
@@ -9869,7 +9852,6 @@ def align(
                 join=join,
                 axis=axis,
                 level=level,
-                copy=copy,
                 fill_value=fill_value,
                 method=method,
                 limit=limit,
@@ -9903,7 +9885,6 @@ def _align_frame(
         join: AlignJoin = "outer",
         axis: Axis | None = None,
         level=None,
-        copy: bool | None = None,
         fill_value=None,
         method=None,
         limit: int | None = None,
@@ -9936,12 +9917,11 @@ def _align_frame(
             reindexers = {0: [join_index, ilidx], 1: [join_columns, clidx]}
 
         left = self._reindex_with_indexers(
-            reindexers, copy=copy, fill_value=fill_value, allow_dups=True
+            reindexers, fill_value=fill_value, allow_dups=True
         )
         # other must be always DataFrame
         right = other._reindex_with_indexers(
             {0: [join_index, iridx], 1: [join_columns, cridx]},
-            copy=copy,
             fill_value=fill_value,
             allow_dups=True,
         )
@@ -9959,14 +9939,12 @@ def _align_series(
         join: AlignJoin = "outer",
         axis: Axis | None = None,
         level=None,
-        copy: bool | None = None,
         fill_value=None,
         method=None,
         limit: int | None = None,
         fill_axis: Axis = 0,
     ) -> tuple[Self, Series, Index | None]:
         is_series = isinstance(self, ABCSeries)
-        copy = False
 
         if (not is_series and axis is None) or axis not in [None, 0, 1]:
             raise ValueError("Must specify axis=0 or 1")
@@ -9987,9 +9965,9 @@ def _align_series(
             if is_series:
                 left = self._reindex_indexer(join_index, lidx)
             elif lidx is None or join_index is None:
-                left = self.copy(deep=copy)
+                left = self.copy(deep=False)
             else:
-                new_mgr = self._mgr.reindex_indexer(join_index, lidx, axis=1, copy=copy)
+                new_mgr = self._mgr.reindex_indexer(join_index, lidx, axis=1)
                 left = self._constructor_from_mgr(new_mgr, axes=new_mgr.axes)
 
             right = other._reindex_indexer(join_index, ridx)
@@ -10008,13 +9986,10 @@ def _align_series(
                 bm_axis = self._get_block_manager_axis(1)
                 fdata = fdata.reindex_indexer(join_index, lidx, axis=bm_axis)
 
-            if copy and fdata is self._mgr:
-                fdata = fdata.copy()
-
             left = self._constructor_from_mgr(fdata, axes=fdata.axes)
 
             if ridx is None:
-                right = other.copy(deep=copy)
+                right = other.copy(deep=False)
             else:
                 right = other.reindex(join_index, level=level)
 
@@ -10059,7 +10034,7 @@ def _where(
                     copy=False,
                 )
                 cond.columns = self.columns
-            cond = cond.align(self, join="right", copy=False)[0]
+            cond = cond.align(self, join="right")[0]
         else:
             if not hasattr(cond, "shape"):
                 cond = np.asanyarray(cond)
@@ -10076,7 +10051,7 @@ def _where(
                 category=FutureWarning,
             )
             cond = cond.fillna(fill_value)
-        cond = cond.infer_objects(copy=False)
+        cond = cond.infer_objects()
 
         msg = "Boolean array expected for the condition, not {dtype}"
 
@@ -10100,7 +10075,7 @@ def _where(
             cond = cond.astype(bool)
 
         cond = -cond if inplace else cond
-        cond = cond.reindex(self._info_axis, axis=self._info_axis_number, copy=False)
+        cond = cond.reindex(self._info_axis, axis=self._info_axis_number)
 
         # try to align with other
         if isinstance(other, NDFrame):
@@ -10113,7 +10088,6 @@ def _where(
                     axis=axis,
                     level=level,
                     fill_value=None,
-                    copy=False,
                 )[1]
 
                 # if we are NOT aligned, raise as we cannot where index
@@ -10925,7 +10899,7 @@ def _tz_convert(ax, tz):
             ax = _tz_convert(ax, tz)
 
         result = self.copy(deep=False)
-        result = result.set_axis(ax, axis=axis, copy=False)
+        result = result.set_axis(ax, axis=axis)
         return result.__finalize__(self, method="tz_convert")
 
     @final
@@ -11131,7 +11105,7 @@ def _tz_localize(ax, tz, ambiguous, nonexistent):
             ax = _tz_localize(ax, tz, ambiguous, nonexistent)
 
         result = self.copy(deep=False)
-        result = result.set_axis(ax, axis=axis, copy=False)
+        result = result.set_axis(ax, axis=axis)
         return result.__finalize__(self, method="tz_localize")
 
     # ----------------------------------------------------------------------
diff --git a/pandas/core/groupby/groupby.py b/pandas/core/groupby/groupby.py
index afd37ca684a08..c10ea9636cba5 100644
--- a/pandas/core/groupby/groupby.py
+++ b/pandas/core/groupby/groupby.py
@@ -1937,9 +1937,7 @@ def _wrap_transform_fast_result(self, result: NDFrameT) -> NDFrameT:
             # Don't convert indices: negative indices need to give rise
             # to null values in the result
             new_ax = result.index.take(ids)
-            output = result._reindex_with_indexers(
-                {0: (new_ax, ids)}, allow_dups=True, copy=False
-            )
+            output = result._reindex_with_indexers({0: (new_ax, ids)}, allow_dups=True)
             output = output.set_axis(obj.index, axis=0)
         return output
 
diff --git a/pandas/core/indexing.py b/pandas/core/indexing.py
index 4ccac6449d835..b127f62faf827 100644
--- a/pandas/core/indexing.py
+++ b/pandas/core/indexing.py
@@ -1330,7 +1330,7 @@ def _multi_take(self, tup: tuple):
             axis: self._get_listlike_indexer(key, axis)
             for (key, axis) in zip(tup, self.obj._AXIS_ORDERS)
         }
-        return self.obj._reindex_with_indexers(d, copy=True, allow_dups=True)
+        return self.obj._reindex_with_indexers(d, allow_dups=True)
 
     # -------------------------------------------------------------------
 
@@ -1362,7 +1362,7 @@ def _getitem_iterable(self, key, axis: AxisInt):
         # A collection of keys
         keyarr, indexer = self._get_listlike_indexer(key, axis)
         return self.obj._reindex_with_indexers(
-            {axis: [keyarr, indexer]}, copy=True, allow_dups=True
+            {axis: [keyarr, indexer]}, allow_dups=True
         )
 
     def _getitem_tuple(self, tup: tuple):
diff --git a/pandas/core/internals/blocks.py b/pandas/core/internals/blocks.py
index df5c0112cfdd1..af529c837089a 100644
--- a/pandas/core/internals/blocks.py
+++ b/pandas/core/internals/blocks.py
@@ -16,10 +16,7 @@
 
 import numpy as np
 
-from pandas._config import (
-    get_option,
-    using_copy_on_write,
-)
+from pandas._config import get_option
 
 from pandas._libs import (
     NaT,
@@ -2612,7 +2609,7 @@ def external_values(values: ArrayLike) -> ArrayLike:
         # Avoid raising in .astype in casting from dt64tz to dt64
         values = values._ndarray
 
-    if isinstance(values, np.ndarray) and using_copy_on_write():
+    if isinstance(values, np.ndarray):
         values = values.view()
         values.flags.writeable = False
 
diff --git a/pandas/core/internals/concat.py b/pandas/core/internals/concat.py
index af16a4175319d..d833dab5b820f 100644
--- a/pandas/core/internals/concat.py
+++ b/pandas/core/internals/concat.py
@@ -185,7 +185,6 @@ def _maybe_reindex_columns_na_proxy(
                 axes[i],
                 indexers[i],
                 axis=i,
-                copy=False,
                 only_slice=True,  # only relevant for i==0
                 allow_dups=True,
                 use_na_proxy=True,  # only relevant for i==0
diff --git a/pandas/core/internals/managers.py b/pandas/core/internals/managers.py
index d3ea5b4af3af1..4e05da8ae9c98 100644
--- a/pandas/core/internals/managers.py
+++ b/pandas/core/internals/managers.py
@@ -19,8 +19,6 @@
 
 import numpy as np
 
-from pandas._config import using_copy_on_write
-
 from pandas._libs import (
     algos as libalgos,
     internals as libinternals,
@@ -599,7 +597,7 @@ def diff(self, n: int) -> Self:
         # only reached with self.ndim == 2
         return self.apply("diff", n=n)
 
-    def astype(self, dtype, copy: bool | None = False, errors: str = "raise") -> Self:
+    def astype(self, dtype, errors: str = "raise") -> Self:
         return self.apply("astype", dtype=dtype, errors=errors)
 
     def convert(self) -> Self:
@@ -720,14 +718,7 @@ def copy(self, deep: bool | None | Literal["all"] = True) -> Self:
         -------
         BlockManager
         """
-        if deep is None:
-            if using_copy_on_write():
-                # use shallow copy
-                deep = False
-            else:
-                # preserve deep copy for BlockManager with copy=None
-                deep = True
-
+        deep = deep if deep is not None else False
         # this preserves the notion of view copying of axes
         if deep:
             # hit in e.g. tests.io.json.test_pandas
@@ -793,7 +784,6 @@ def reindex_axis(
             indexer,
             axis=axis,
             fill_value=fill_value,
-            copy=False,
             only_slice=only_slice,
         )
 
@@ -804,7 +794,6 @@ def reindex_indexer(
         axis: AxisInt,
         fill_value=None,
         allow_dups: bool = False,
-        copy: bool | None = True,
         only_slice: bool = False,
         *,
         use_na_proxy: bool = False,
@@ -817,8 +806,6 @@ def reindex_indexer(
         axis : int
         fill_value : object, default None
         allow_dups : bool, default False
-        copy : bool or None, default True
-            If None, regard as False to get shallow copy.
         only_slice : bool, default False
             Whether to take views, not copies, along columns.
         use_na_proxy : bool, default False
@@ -826,19 +813,11 @@ def reindex_indexer(
 
         pandas-indexer with -1's only.
         """
-        if copy is None:
-            if using_copy_on_write():
-                # use shallow copy
-                copy = False
-            else:
-                # preserve deep copy for BlockManager with copy=None
-                copy = True
-
         if indexer is None:
-            if new_axis is self.axes[axis] and not copy:
+            if new_axis is self.axes[axis]:
                 return self
 
-            result = self.copy(deep=copy)
+            result = self.copy(deep=False)
             result.axes = list(self.axes)
             result.axes[axis] = new_axis
             return result
@@ -1076,7 +1055,6 @@ def take(
             indexer=indexer,
             axis=axis,
             allow_dups=True,
-            copy=None,
         )
 
 
@@ -1463,10 +1441,7 @@ def _iset_single(
         # Caller is responsible for verifying value.shape
 
         if inplace and blk.should_store(value):
-            copy = False
-            if not self._has_no_reference_block(blkno):
-                # perform Copy-on-Write and clear the reference
-                copy = True
+            copy = not self._has_no_reference_block(blkno)
             iloc = self.blklocs[loc]
             blk.set_inplace(slice(iloc, iloc + 1), value, copy=copy)
             return
diff --git a/pandas/core/reshape/merge.py b/pandas/core/reshape/merge.py
index 4f10fd729723e..0494138d1e16f 100644
--- a/pandas/core/reshape/merge.py
+++ b/pandas/core/reshape/merge.py
@@ -163,7 +163,6 @@ def merge(
             suffixes=suffixes,
             indicator=indicator,
             validate=validate,
-            copy=copy,
         )
     else:
         op = _MergeOperation(
@@ -180,7 +179,7 @@ def merge(
             indicator=indicator,
             validate=validate,
         )
-        return op.get_result(copy=copy)
+        return op.get_result()
 
 
 def _cross_merge(
@@ -193,7 +192,6 @@ def _cross_merge(
     right_index: bool = False,
     sort: bool = False,
     suffixes: Suffixes = ("_x", "_y"),
-    copy: bool | None = None,
     indicator: str | bool = False,
     validate: str | None = None,
 ) -> DataFrame:
@@ -232,7 +230,6 @@ def _cross_merge(
         suffixes=suffixes,
         indicator=indicator,
         validate=validate,
-        copy=copy,
     )
     del res[cross_col]
     return res
@@ -291,7 +288,7 @@ def _groupby_and_merge(
     from pandas.core.reshape.concat import concat
 
     result = concat(pieces, ignore_index=True)
-    result = result.reindex(columns=pieces[0].columns, copy=False)
+    result = result.reindex(columns=pieces[0].columns)
     return result, lby
 
 
@@ -708,7 +705,6 @@ def merge_asof(
 
 
 # TODO: transformations??
-# TODO: only copy DataFrames when modification necessary
 class _MergeOperation:
     """
     Perform a database (SQL) merge operation between two DataFrame or Series
@@ -726,7 +722,6 @@ class _MergeOperation:
     right_index: bool
     sort: bool
     suffixes: Suffixes
-    copy: bool
     indicator: str | bool
     validate: str | None
     join_names: list[Hashable]
@@ -827,7 +822,6 @@ def _reindex_and_concat(
         join_index: Index,
         left_indexer: npt.NDArray[np.intp] | None,
         right_indexer: npt.NDArray[np.intp] | None,
-        copy: bool | None,
     ) -> DataFrame:
         """
         reindex along index and concat along columns.
@@ -848,7 +842,6 @@ def _reindex_and_concat(
                 join_index,
                 left_indexer,
                 axis=1,
-                copy=False,
                 only_slice=True,
                 allow_dups=True,
                 use_na_proxy=True,
@@ -863,7 +856,6 @@ def _reindex_and_concat(
                 join_index,
                 right_indexer,
                 axis=1,
-                copy=False,
                 only_slice=True,
                 allow_dups=True,
                 use_na_proxy=True,
@@ -875,18 +867,16 @@ def _reindex_and_concat(
 
         left.columns = llabels
         right.columns = rlabels
-        result = concat([left, right], axis=1, copy=copy)
+        result = concat([left, right], axis=1)
         return result
 
-    def get_result(self, copy: bool | None = True) -> DataFrame:
+    def get_result(self) -> DataFrame:
         if self.indicator:
             self.left, self.right = self._indicator_pre_merge(self.left, self.right)
 
         join_index, left_indexer, right_indexer = self._get_join_info()
 
-        result = self._reindex_and_concat(
-            join_index, left_indexer, right_indexer, copy=copy
-        )
+        result = self._reindex_and_concat(join_index, left_indexer, right_indexer)
         result = result.__finalize__(self, method=self._merge_type)
 
         if self.indicator:
@@ -1920,7 +1910,7 @@ def __init__(
             sort=True,  # factorize sorts
         )
 
-    def get_result(self, copy: bool | None = True) -> DataFrame:
+    def get_result(self) -> DataFrame:
         join_index, left_indexer, right_indexer = self._get_join_info()
 
         left_join_indexer: npt.NDArray[np.intp] | None
@@ -1942,7 +1932,7 @@ def get_result(self, copy: bool | None = True) -> DataFrame:
             raise ValueError("fill_method must be 'ffill' or None")
 
         result = self._reindex_and_concat(
-            join_index, left_join_indexer, right_join_indexer, copy=copy
+            join_index, left_join_indexer, right_join_indexer
         )
         self._maybe_add_join_keys(result, left_indexer, right_indexer)
 
@@ -2308,7 +2298,7 @@ def _get_multiindex_indexer(
     if sort:
         rcodes = list(map(np.take, rcodes, index.codes))
     else:
-        i8copy = lambda a: a.astype("i8", subok=False, copy=True)
+        i8copy = lambda a: a.astype("i8", subok=False)
         rcodes = list(map(i8copy, index.codes))
 
     # fix right labels if there were any nulls
diff --git a/pandas/core/series.py b/pandas/core/series.py
index 65ef7d352a547..df7b6b8f1ab12 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -25,8 +25,6 @@
 
 import numpy as np
 
-from pandas._config import using_copy_on_write
-
 from pandas._libs import (
     lib,
     properties,
@@ -397,7 +395,7 @@ def __init__(
         if copy is None:
             copy = False
 
-        if isinstance(data, SingleBlockManager) and using_copy_on_write() and not copy:
+        if isinstance(data, SingleBlockManager) and not copy:
             data = data.copy(deep=False)
 
             if not allow_mgr:
@@ -432,7 +430,7 @@ def __init__(
         refs = None
         if isinstance(data, Index):
             if dtype is not None:
-                data = data.astype(dtype, copy=False)
+                data = data.astype(dtype)
 
             refs = data._references
             data = data._values
@@ -451,7 +449,7 @@ def __init__(
                 index = data.index
                 data = data._mgr.copy(deep=False)
             else:
-                data = data.reindex(index, copy=copy)
+                data = data.reindex(index)
                 copy = False
                 data = data._mgr
         elif is_dict_like(data):
@@ -498,7 +496,7 @@ def __init__(
         # create/copy the manager
         if isinstance(data, SingleBlockManager):
             if dtype is not None:
-                data = data.astype(dtype=dtype, errors="ignore", copy=copy)
+                data = data.astype(dtype=dtype, errors="ignore")
             elif copy:
                 data = data.copy()
         else:
@@ -568,7 +566,7 @@ def _init_dict(
 
         # Now we just make sure the order is respected, if any
         if data and index is not None:
-            s = s.reindex(index, copy=False)
+            s = s.reindex(index)
         return s._mgr, s.index
 
     # ----------------------------------------------------------------------
@@ -2664,7 +2662,7 @@ def corr(
         >>> s1.corr(s2)
         -1.0
         """  # noqa: E501
-        this, other = self.align(other, join="inner", copy=False)
+        this, other = self.align(other, join="inner")
         if len(this) == 0:
             return np.nan
 
@@ -2721,7 +2719,7 @@ def cov(
         >>> s1.cov(s2)
         -0.01685762652715874
         """
-        this, other = self.align(other, join="inner", copy=False)
+        this, other = self.align(other, join="inner")
         if len(this) == 0:
             return np.nan
         this_values = this.to_numpy(dtype=float, na_value=np.nan, copy=False)
@@ -2923,8 +2921,8 @@ def dot(self, other: AnyArrayLike) -> Series | np.ndarray:
             if len(common) > len(self.index) or len(common) > len(other.index):
                 raise ValueError("matrices are not aligned")
 
-            left = self.reindex(index=common, copy=False)
-            right = other.reindex(index=common, copy=False)
+            left = self.reindex(index=common)
+            right = other.reindex(index=common)
             lvals = left.values
             rvals = right.values
         else:
@@ -3235,13 +3233,13 @@ def combine_first(self, other) -> Series:
         keep_other = other.index.difference(this.index[notna(this)])
         keep_this = this.index.difference(keep_other)
 
-        this = this.reindex(keep_this, copy=False)
-        other = other.reindex(keep_other, copy=False)
+        this = this.reindex(keep_this)
+        other = other.reindex(keep_other)
 
         if this.dtype.kind == "M" and other.dtype.kind != "M":
             other = to_datetime(other)
         combined = concat([this, other])
-        combined = combined.reindex(new_index, copy=False)
+        combined = combined.reindex(new_index)
         return combined.__finalize__(self, method="combine_first")
 
     def update(self, other: Series | Sequence | Mapping) -> None:
@@ -3552,7 +3550,7 @@ def sort_values(
         if is_range_indexer(sorted_index, len(sorted_index)):
             if inplace:
                 return self._update_inplace(self)
-            return self.copy(deep=None)
+            return self.copy(deep=False)
 
         result = self._constructor(
             self._values[sorted_index], index=self.index[sorted_index], copy=False
@@ -4185,7 +4183,7 @@ def reorder_levels(self, order: Sequence[Level]) -> Series:
         if not isinstance(self.index, MultiIndex):  # pragma: no cover
             raise Exception("Can only reorder levels on a hierarchical axis.")
 
-        result = self.copy(deep=None)
+        result = self.copy(deep=False)
         assert isinstance(result.index, MultiIndex)
         result.index = result.index.reorder_levels(order)
         return result
@@ -4777,7 +4775,6 @@ def rename(
             # Hashable], Callable[[Any], Hashable], None]"
             return super()._rename(
                 index,  # type: ignore[arg-type]
-                copy=copy,
                 inplace=inplace,
                 level=level,
                 errors=errors,
@@ -4818,7 +4815,7 @@ def set_axis(
         axis: Axis = 0,
         copy: bool | None = None,
     ) -> Series:
-        return super().set_axis(labels, axis=axis, copy=copy)
+        return super().set_axis(labels, axis=axis)
 
     # error: Cannot determine type of 'reindex'
     @doc(
@@ -4841,7 +4838,6 @@ def reindex(  # type: ignore[override]
         return super().reindex(
             index=index,
             method=method,
-            copy=copy,
             level=level,
             fill_value=fill_value,
             limit=limit,
@@ -4958,7 +4954,6 @@ def rename_axis(
             mapper=mapper,
             index=index,
             axis=axis,
-            copy=copy,
             inplace=inplace,
         )
 
@@ -5488,7 +5483,7 @@ def case_when(
             )
             for condition, replacement in caselist
         ]
-        default = self.copy()
+        default = self.copy(deep=False)
         conditions, replacements = zip(*caselist)
         common_dtypes = [infer_dtype_from(arg)[0] for arg in [*replacements, default]]
         if len(set(common_dtypes)) > 1:
@@ -5652,7 +5647,7 @@ def dropna(
             result = remove_na_arraylike(self)
         else:
             if not inplace:
-                result = self.copy(deep=None)
+                result = self.copy(deep=False)
             else:
                 result = self
 
@@ -5913,7 +5908,7 @@ def _align_for_op(self, right, align_asobject: bool = False):
                     left = left.astype(object)
                     right = right.astype(object)
 
-                left, right = left.align(right, copy=False)
+                left, right = left.align(right)
 
         return left, right
 
@@ -5939,7 +5934,7 @@ def _binop(self, other: Series, func, level=None, fill_value=None) -> Series:
         this = self
 
         if not self.index.equals(other.index):
-            this, other = self.align(other, level=level, join="outer", copy=False)
+            this, other = self.align(other, level=level, join="outer")
 
         this_vals, other_vals = ops.fill_binop(this._values, other._values, fill_value)