matplotlib
diff --git a/‎lib/matplotlib/_constrained_layout.py
+10-5 b/‎lib/matplotlib/_constrained_layout.py
+10-5
diff --git a/‎lib/matplotlib/_layoutgrid.py
+11-8 b/‎lib/matplotlib/_layoutgrid.py
+11-8
@@ -64,7 +64,7 @@
 
 ######################################################
 def do_constrained_layout(fig, h_pad, w_pad,
-                          hspace=None, wspace=None):
+                          hspace=None, wspace=None, rect=(0, 0, 1, 1)):
     """
     Do the constrained_layout.  Called at draw time in
      ``figure.constrained_layout()``
@@ -87,14 +87,18 @@ def do_constrained_layout(fig, h_pad, w_pad,
        of 0.1 of the figure width between each column.
        If h/wspace < h/w_pad, then the pads are used instead.
 
+    rect : tuple of 4 floats
+        Rectangle in figure coordinates to perform constrained layout in
+        [left, bottom, width, height], each from 0-1.
+
     Returns
     -------
     layoutgrid : private debugging structure
     """
 
     renderer = _get_renderer(fig)
     # make layoutgrid tree...
-    layoutgrids = make_layoutgrids(fig, None)
+    layoutgrids = make_layoutgrids(fig, None, rect=rect)
     if not layoutgrids['hasgrids']:
         _api.warn_external('There are no gridspecs with layoutgrids. '
                            'Possibly did not call parent GridSpec with the'
@@ -133,7 +137,7 @@ def do_constrained_layout(fig, h_pad, w_pad,
     return layoutgrids
 
 
-def make_layoutgrids(fig, layoutgrids):
+def make_layoutgrids(fig, layoutgrids, rect=[0, 0, 1, 1]):
     """
     Make the layoutgrid tree.
 
@@ -147,8 +151,9 @@ def make_layoutgrids(fig, layoutgrids):
         layoutgrids = dict()
         layoutgrids['hasgrids'] = False
     if not hasattr(fig, '_parent'):
-        # top figure
-        layoutgrids[fig] = mlayoutgrid.LayoutGrid(parent=None, name='figlb')
+        # top figure;  pass rect as parent to allow user-specified
+        # margins
+        layoutgrids[fig] = mlayoutgrid.LayoutGrid(parent=rect, name='figlb')
     else:
         # subfigure
         gs = fig._subplotspec.get_gridspec()
 
@@ -39,7 +39,7 @@ def __init__(self, parent=None, parent_pos=(0, 0),
         self.parent_pos = parent_pos
         self.parent_inner = parent_inner
         self.name = name + seq_id()
-        if parent is not None:
+        if isinstance(parent, LayoutGrid):
             self.name = f'{parent.name}.{self.name}'
         self.nrows = nrows
         self.ncols = ncols
@@ -51,8 +51,10 @@ def __init__(self, parent=None, parent_pos=(0, 0),
             self.width_ratios = np.ones(ncols)
 
         sn = self.name + '_'
-        if parent is None:
-            self.parent = None
+        if not isinstance(parent, LayoutGrid):
+            # parent can be a rect if not a LayoutGrid
+            # allows specifying a rectangle to contain the layout.
+            self.parent = parent
             self.solver = kiwi.Solver()
         else:
             self.parent = parent
@@ -178,12 +180,13 @@ def parent_constraints(self):
         # parent's left, the last column right equal to the
         # parent's right...
         parent = self.parent
-        if parent is None:
-            hc = [self.lefts[0] == 0,
-                  self.rights[-1] == 1,
+        if not isinstance(parent, LayoutGrid):
+            # specify a rectangle in figure coordinates
+            hc = [self.lefts[0] == parent[0],
+                  self.rights[-1] == parent[0] + parent[2],
                   # top and bottom reversed order...
-                  self.tops[0] == 1,
-                  self.bottoms[-1] == 0]
+                  self.tops[0] == parent[1] + parent[3],
+                  self.bottoms[-1] == parent[1]]
         else:
             rows, cols = self.parent_pos
             rows = np.atleast_1d(rows)