diff --git a/Doc/library/io.rst b/Doc/library/io.rst
--- a/Doc/library/io.rst
+++ b/Doc/library/io.rst
@@ -353,6 +353,11 @@
       is usual for each of the lines provided to have a line separator at the
       end.
 
+   .. method:: __del__()
+
+      Prepare for object destruction. :class:`IOBase` provides a
+      default implementation of this method that calls the instance's
+      :meth:`~IOBase.close` method.
 
 .. class:: RawIOBase