diff --git a/Doc/library/json.rst b/Doc/library/json.rst
--- a/Doc/library/json.rst
+++ b/Doc/library/json.rst
@@ -608,11 +608,17 @@ Command line options
 
    If *infile* is not specified, read from :attr:`sys.stdin`.
 
 .. cmdoption:: outfile
 
    Write the output of the *infile* to the given *outfile*. Otherwise, write it
    to :attr:`sys.stdout`.
 
+.. cmdoption:: --unsorted
+
+   Do not sort the output of dictionaries by their key.
+
+   .. versionadded:: 3.5
+
 .. cmdoption:: -h, --help
 
    Show the help message.
diff --git a/Lib/json/tool.py b/Lib/json/tool.py
--- a/Lib/json/tool.py
+++ b/Lib/json/tool.py
@@ -19,24 +19,28 @@ def main():
     prog = 'python -m json.tool'
     description = ('A simple command line interface for json module '
                    'to validate and pretty-print JSON objects.')
     parser = argparse.ArgumentParser(prog=prog, description=description)
     parser.add_argument('infile', nargs='?', type=argparse.FileType(),
                         help='a JSON file to be validated or pretty-printed')
     parser.add_argument('outfile', nargs='?', type=argparse.FileType('w'),
                         help='write the output of infile to outfile')
+    parser.add_argument('--unsorted', dest='sort_keys', action='store_true',
+                        default=False, help='do not sort the output of '
+                                            'dictionaries by their key.')
     options = parser.parse_args()
 
     infile = options.infile or sys.stdin
     outfile = options.outfile or sys.stdout
+    sort_keys = not options.sort_keys
     with infile:
         try:
             obj = json.load(infile)
         except ValueError as e:
             raise SystemExit(e)
     with outfile:
-        json.dump(obj, outfile, sort_keys=True, indent=4)
+        json.dump(obj, outfile, sort_keys=sort_keys, indent=4)
         outfile.write('\n')
 
 
 if __name__ == '__main__':
     main()
diff --git a/Lib/test/test_json/test_tool.py b/Lib/test/test_json/test_tool.py
--- a/Lib/test/test_json/test_tool.py
+++ b/Lib/test/test_json/test_tool.py
@@ -32,16 +32,38 @@ class TestTool(unittest.TestCase):
         },
         {
             "field": "yes",
             "morefield": false
         }
     ]
     """)
 
+    expect_without_sort_keys = textwrap.dedent("""\
+    [
+        [
+            "blorpie"
+        ],
+        [
+            "whoops"
+        ],
+        [],
+        "d-shtaeou",
+        "d-nthiouh",
+        "i-vhbjkhnth",
+        {
+            "nifty": 87
+        },
+        {
+            "morefield": false,
+            "field": "yes"
+        }
+    ]
+    """)
+
     def test_stdin_stdout(self):
         with subprocess.Popen(
                 (sys.executable, '-m', 'json.tool'),
                 stdin=subprocess.PIPE, stdout=subprocess.PIPE) as proc:
             out, err = proc.communicate(self.data.encode())
         self.assertEqual(out.splitlines(), self.expect.encode().splitlines())
         self.assertEqual(err, None)
 
@@ -70,8 +92,20 @@ class TestTool(unittest.TestCase):
         self.assertEqual(out, b'')
         self.assertEqual(err, b'')
 
     def test_help_flag(self):
         rc, out, err = assert_python_ok('-m', 'json.tool', '-h')
         self.assertEqual(rc, 0)
         self.assertTrue(out.startswith(b'usage: '))
         self.assertEqual(err, b'')
+
+    def test_unsorted_flag(self):
+        infile = self._create_infile()
+        outfile = support.TESTFN + '_unsorted.out'
+        rc, out, err = assert_python_ok('-m', 'json.tool', infile, outfile,
+                                        '--unsorted')
+        self.addCleanup(os.remove, outfile)
+        with open(outfile, "r") as fp:
+            self.assertEqual(fp.read(), self.expect_without_sort_keys)
+        self.assertEqual(rc, 0)
+        self.assertEqual(out, b'')
+        self.assertEqual(err, b'')