diff --git a/Lib/cgi.py b/Lib/cgi.py
index 4de82ea6df9..b6fd4074546 100755
--- a/Lib/cgi.py
+++ b/Lib/cgi.py
@@ -552,6 +552,12 @@ def __init__(self, fp=None, headers=None, outerboundary=b'',
         else:
             self.read_single()
 
+    def __del__(self):
+        try:
+            self.file.close()
+        except AttributeError:
+            pass
+
     def __repr__(self):
         """Return a printable representation."""
         return "FieldStorage(%r, %r, %r)" % (
diff --git a/Misc/NEWS b/Misc/NEWS
index 431674abbd5..125d604697c 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -38,6 +38,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #18394: Close cgi.FieldStorage's optional file.
+
 - Issue #17702: On error, os.environb now removes suppress the except context
   when raising a new KeyError with the original key.