diff --git a/doc/api/next_api_changes/2018-09-27-AL.rst b/doc/api/next_api_changes/2018-09-27-AL.rst
new file mode 100644
index 000000000000..f938332b776c
--- /dev/null
+++ b/doc/api/next_api_changes/2018-09-27-AL.rst
@@ -0,0 +1,4 @@
+Passing 'normal' to `Axes.axis()` is deprecated
+```````````````````````````````````````````````
+
+Use ``axis('auto')`` instead.
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
index 712c9f097371..210f611f07af 100644
--- a/lib/matplotlib/axes/_base.py
+++ b/lib/matplotlib/axes/_base.py
@@ -1263,7 +1263,8 @@ def set_aspect(self, aspect, adjustable=None, anchor=None, share=False):
         matplotlib.axes.Axes.set_anchor
             defining the position in case of extra space.
         """
-        if not (isinstance(aspect, str) and aspect in ('equal', 'auto')):
+        if not (cbook._str_equal(aspect, 'equal')
+                or cbook._str_equal(aspect, 'auto')):
             aspect = float(aspect)  # raise ValueError if necessary
         if share:
             axes = set(self._shared_x_axes.get_siblings(self)
@@ -1645,6 +1646,10 @@ def axis(self, *v, **kwargs):
                 self.set_axis_off()
             elif s in ('equal', 'tight', 'scaled', 'normal',
                        'auto', 'image', 'square'):
+                if s == 'normal':
+                    cbook.warn_deprecated(
+                        "3.1", "Passing 'normal' to axis() is deprecated "
+                        "since %(version)s; use 'auto' instead.")
                 self.set_autoscale_on(True)
                 self.set_aspect('auto')
                 self.autoscale_view(tight=False)