matplotlib · FazeelUsmani · Apr 7, 2026 · Apr 7, 2026
diff --git a/doc/api/next_api_changes/behavior/19029-FU.rst b/doc/api/next_api_changes/behavior/19029-FU.rst
@@ -0,0 +1,11 @@
+y-axis labels with non-default rotation no longer overlap tick labels
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Setting a y-axis label with a rotation other than the default (e.g.
+``ax.set_ylabel("...", rotation=270)``, or ``cbar.set_label("...",
+rotation=270)`` on a colorbar) previously could cause the label to
+overlap the tick labels because the automatic label placement assumed a
+90° rotation. The label position is now computed from the rendered
+label's actual extent, so it sits clear of the tick labels for any
+rotation. This may shift the position of y-labels that use non-default
+rotations.
diff --git a/lib/matplotlib/axis.py b/lib/matplotlib/axis.py
@@ -2735,14 +2735,27 @@ def _update_label_position(self, renderer):
             # Union with extents of the left spine if present, of the axes otherwise.
             bbox = mtransforms.Bbox.union([
                 *bboxes, self.axes.spines.get("left", self.axes).get_window_extent()])
-            self.label.set_position(
-                (bbox.x0 - self.labelpad * self.get_figure(root=True).dpi / 72, y))
+            target_x = bbox.x0 - self.labelpad * self.get_figure(root=True).dpi / 72
+            self.label.set_position((target_x, y))
+            # The vertical alignment set in `set_label_position` assumes a
+            # 90° rotation; for any other rotation the rotated label may
+            # extend back toward the tick labels and overlap them. Shift
+            # the label outward by the overhang. See issue #19029.
+            label_bbox = self.label.get_window_extent(renderer)
+            overhang = label_bbox.x1 - target_x
+            if overhang > 0:
+                self.label.set_position((target_x - overhang, y))
         else:
             # Union with extents of the right spine if present, of the axes otherwise.
             bbox = mtransforms.Bbox.union([
                 *bboxes2, self.axes.spines.get("right", self.axes).get_window_extent()])
-            self.label.set_position(
-                (bbox.x1 + self.labelpad * self.get_figure(root=True).dpi / 72, y))
+            target_x = bbox.x1 + self.labelpad * self.get_figure(root=True).dpi / 72
+            self.label.set_position((target_x, y))
+            # See comment in the 'left' branch above (issue #19029).
+            label_bbox = self.label.get_window_extent(renderer)
+            overhang = target_x - label_bbox.x0
+            if overhang > 0:
+                self.label.set_position((target_x + overhang, y))
 
     def _update_offset_text_position(self, bboxes, bboxes2):
         """

diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -9070,6 +9070,56 @@ def test_ylabel_ha_with_position(ha):
     assert ax.yaxis.label.get_ha() == ha
 
 
+@pytest.mark.parametrize('label_position', ['left', 'right'])
+@pytest.mark.parametrize('rotation', [0, 45, 90, 135, 180, 270, -90])
+def test_ylabel_no_overlap_with_ticklabels(label_position, rotation):
+    """Regression test for #19029: a y-label with rotation other than 90°
+    must not overlap the tick labels regardless of label_position.
+    """
+    fig, ax = plt.subplots()
+    ax.plot([1, 3, 2])
+    ax.yaxis.set_label_position(label_position)
+    if label_position == 'right':
+        ax.yaxis.tick_right()
+    ax.set_ylabel("test label", rotation=rotation)
+    fig.canvas.draw()
+    renderer = fig.canvas.get_renderer()
+    label_bbox = ax.yaxis.label.get_window_extent(renderer)
+    tick_bboxes = [t.get_window_extent(renderer)
+                   for t in ax.yaxis.get_ticklabels() if t.get_visible()]
+    tick_union = mtransforms.Bbox.union(tick_bboxes)
+    if label_position == 'right':
+        assert label_bbox.x0 >= tick_union.x1
+    else:
+        assert label_bbox.x1 <= tick_union.x0
+
+
+@pytest.mark.parametrize('label_position', ['left', 'right'])
+def test_align_ylabels_mixed_rotation(label_position):
+    """Issue #19029: ``fig.align_ylabels`` must keep two y-labels visually
+    aligned even when they use different rotations. The per-axis overhang
+    correction in `_update_label_position` shifts each axis independently;
+    this test guards against that breaking sibling alignment.
+    """
+    fig, axs = plt.subplots(2, figsize=(4, 6))
+    for ax in axs:
+        ax.plot([1, 30, 2])
+        ax.yaxis.set_label_position(label_position)
+        if label_position == 'right':
+            ax.yaxis.tick_right()
+    axs[0].set_ylabel('first', rotation=90)
+    axs[1].set_ylabel('second', rotation=270)
+    fig.align_ylabels(axs)
+    fig.canvas.draw()
+    renderer = fig.canvas.get_renderer()
+    bbox0 = axs[0].yaxis.label.get_window_extent(renderer)
+    bbox1 = axs[1].yaxis.label.get_window_extent(renderer)
+    # Both visible label bboxes should occupy the same horizontal range,
+    # even though the underlying anchor positions differ between rotations.
+    assert bbox0.x0 == pytest.approx(bbox1.x0, abs=0.5)
+    assert bbox0.x1 == pytest.approx(bbox1.x1, abs=0.5)
+
+
 def test_bar_label_location_vertical():
     ax = plt.gca()
     xs, heights = [1, 2], [3, -4]

diff --git a/lib/matplotlib/tests/test_colorbar.py b/lib/matplotlib/tests/test_colorbar.py
@@ -733,6 +733,25 @@ def test_colorbar_label():
     assert cbar3.ax.get_xlabel() == 'horizontal cbar'
 
 
+def test_colorbar_label_rotation_no_overlap():
+    """Smoke test for #19029: a rotation=270 colorbar label must not
+    overlap negative tick labels (the original user-facing symptom).
+    """
+    fig, ax = plt.subplots()
+    im = ax.imshow([[-100, 0], [50, 100]])
+    cbar = fig.colorbar(im, ax=ax)
+    cbar.set_label('RT(1ax) - RT(2ax) [ms]', rotation=270)
+    fig.canvas.draw()
+    renderer = fig.canvas.get_renderer()
+    label_bbox = cbar.ax.yaxis.label.get_window_extent(renderer)
+    # Colorbar labels live on the right, so the label must sit clear of
+    # the rightmost visible tick-label edge.
+    tick_x1_max = max(t.get_window_extent(renderer).x1
+                      for t in cbar.ax.yaxis.get_ticklabels()
+                      if t.get_visible())
+    assert label_bbox.x0 >= tick_x1_max
+
+
 # TODO: tighten tolerance after baseline image is regenerated for text overhaul
 @image_comparison(['colorbar_keeping_xlabel.png'], style='mpl20', tol=0.03)
 def test_keeping_xlabel():