From 2f9ef9ec0dfbe04b95acd69ba8327779856ef503 Mon Sep 17 00:00:00 2001
From: Matthew Roeschke <10647082+mroeschke@users.noreply.github.com>
Date: Wed, 7 Feb 2024 11:40:15 -0800
Subject: [PATCH 1/2] BUG: sort_index(1, ignore_index=True, ascending=False)

---
 doc/source/whatsnew/v3.0.0.rst                |  2 +-
 pandas/core/generic.py                        |  5 ++++-
 pandas/tests/frame/methods/test_sort_index.py | 17 +++++++++++++++++
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/doc/source/whatsnew/v3.0.0.rst b/doc/source/whatsnew/v3.0.0.rst
index 2c39318fa28b3..fcf268c15da95 100644
--- a/doc/source/whatsnew/v3.0.0.rst
+++ b/doc/source/whatsnew/v3.0.0.rst
@@ -242,7 +242,7 @@ Styler
 Other
 ^^^^^
 - Bug in :meth:`DataFrame.where` where using a non-bool type array in the function would return a ``ValueError`` instead of a ``TypeError`` (:issue:`56330`)
-
+- Bug in :meth:`DataFrame.sort_index` when passing ``axis="columns"`` and ``ignore_index=True`` and ``ascending=False`` not returning a :class:`RangeIndex` columns (:issue:`57293it `)
 
 .. ***DO NOT USE THIS SECTION***
 
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 93c2afab51d2c..1741c61e7195f 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -5080,7 +5080,10 @@ def sort_index(
                 result = self.copy(deep=None)
 
             if ignore_index:
-                result.index = default_index(len(self))
+                if axis == 1:
+                    result.columns = default_index(len(self.columns))
+                else:
+                    result.index = default_index(len(self))
             if inplace:
                 return None
             else:
diff --git a/pandas/tests/frame/methods/test_sort_index.py b/pandas/tests/frame/methods/test_sort_index.py
index 1a5df0778ec52..d88daaff685aa 100644
--- a/pandas/tests/frame/methods/test_sort_index.py
+++ b/pandas/tests/frame/methods/test_sort_index.py
@@ -1003,6 +1003,23 @@ def test_axis_columns_ignore_index():
     tm.assert_frame_equal(result, expected)
 
 
+def test_axis_columns_ignore_index_ascending_false():
+    # GH 57293
+    df = DataFrame(
+        {
+            "b": [1.0, 3.0, np.nan],
+            "a": [1, 4, 3],
+            1: ["a", "b", "c"],
+            "e": [3, 1, 4],
+            "d": [1, 2, 8],
+        }
+    ).set_index(["b", "a", 1])
+    result = df.sort_index(axis="columns", ignore_index=True, ascending=False)
+    expected = df.copy()
+    expected.columns = RangeIndex(2)
+    tm.assert_frame_equal(result, expected)
+
+
 def test_sort_index_stable_sort():
     # GH 57151
     df = DataFrame(

From 5ef264c7343ae8e528ffcccf58214875a7a57b6e Mon Sep 17 00:00:00 2001
From: Matthew Roeschke <10647082+mroeschke@users.noreply.github.com>
Date: Wed, 7 Feb 2024 12:16:08 -0800
Subject: [PATCH 2/2] Remove error

---
 doc/source/whatsnew/v3.0.0.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/source/whatsnew/v3.0.0.rst b/doc/source/whatsnew/v3.0.0.rst
index fcf268c15da95..503da28684d60 100644
--- a/doc/source/whatsnew/v3.0.0.rst
+++ b/doc/source/whatsnew/v3.0.0.rst
@@ -241,8 +241,8 @@ Styler
 
 Other
 ^^^^^
+- Bug in :meth:`DataFrame.sort_index` when passing ``axis="columns"`` and ``ignore_index=True`` and ``ascending=False`` not returning a :class:`RangeIndex` columns (:issue:`57293`)
 - Bug in :meth:`DataFrame.where` where using a non-bool type array in the function would return a ``ValueError`` instead of a ``TypeError`` (:issue:`56330`)
-- Bug in :meth:`DataFrame.sort_index` when passing ``axis="columns"`` and ``ignore_index=True`` and ``ascending=False`` not returning a :class:`RangeIndex` columns (:issue:`57293it `)
 
 .. ***DO NOT USE THIS SECTION***