diff --git a/llvm/utils/llvm-patch b/llvm/utils/llvm-patch
new file mode 100755
--- /dev/null
+++ b/llvm/utils/llvm-patch
@@ -0,0 +1,148 @@
+#!/usr/bin/env python3
+
+"""
+This script uses the Phabricator API to manage patches. It is currently
+work-in-progress, please double-check the results before pushing changes.
+
+It requires a valid ~/.arcrc file with your API token, e.g.
+
+{
+  "hosts": {
+    "https://reviews.llvm.org/api/": {
+      "token": "cli-thisismyapikey"
+    }
+  }
+}
+
+To get your API token, visit https://reviews.llvm.org/conduit/login/.
+
+TODO:
+  * Support uploading patches.
+  * Better error handling.
+  * Python2 support?
+  * Use a better way to find raw diff IDs instead of using querydiffs.
+  * Support applying a stack of patches.
+"""
+
+import argparse
+import json
+import os.path
+import os
+import subprocess
+import sys
+import tempfile
+import urllib.parse
+import urllib.request
+
+
+def get_api_token():
+    """Get the Phabricator API token for reviews.llvm.org from ~/.arcrc."""
+
+    with open(os.path.expanduser(os.path.join('~', '.arcrc')), 'rt') as f:
+        d = json.loads(f.read())
+        if 'hosts' not in d:
+            print('No hosts in ~/.arcrc found')
+            sys.exit(1)
+        d = d['hosts']
+        if 'https://reviews.llvm.org/api/' not in d:
+            print('No entry for "https://reviews.llvm.org/api/" found in '
+                  '~/.arcrc')
+            sys.exit(1)
+        return d['https://reviews.llvm.org/api/']['token']
+
+
+def api_request(endpoint, values):
+    values['api.token'] = get_api_token()
+    data = urllib.parse.urlencode(values)
+    data = data.encode('ascii')  # data should be bytes
+    req = urllib.request.Request(
+        'https://reviews.llvm.org/api/' + endpoint, data)
+    with urllib.request.urlopen(req) as response:
+        data = json.loads(response.read())
+        if not data['result']:
+            print('ERROR: {}'.format(data['error_info']))
+        return data['result']
+
+
+def should_strip_line(s):
+    return s.startswith('Summary:') or s.startswith(
+        'Subscribers:') or s.startswith('Tags:')
+
+
+def apply_patch(args):
+    """
+    Fetches the latest diff for a given differential ID and applies it to the
+    current working directory.
+    """
+    revision_id = int(args.ID.replace('D', ''))
+
+    # Make sure there are no uncommitted changes.
+    ret = subprocess.call(['git', 'diff-index', '--quiet', 'HEAD'])
+    if ret != 0:
+        print("ERROR: There are uncommitted changes in the repository!\n"
+              "       Can only apply a patch to a clean working directory.")
+        sys.exit(1)
+
+    # Get list of diffs for the requested revision.
+    print('Fetching information for {}.'.format(args.ID))
+    diffquery = api_request('differential.querydiffs', {
+        'revisionIDs[0]': revision_id
+    })
+
+    # Sort diff ids by creation date and get the latest diff id.
+    diff_ids = sorted([(d['id'], int(d['dateCreated']))
+                       for d in diffquery.values()], key=lambda x: x[1])
+    diff_id = diff_ids[-1][0]
+
+    # Fetch raw diff for latest diff id.
+    print('Fetching diff with ID {}.'.format(diff_id))
+    rawdiff = api_request('differential.getrawdiff', {
+        'diffID': diff_id
+    })
+
+    # Get commit message and strip unnecessary lines (Summary:, Subscribers:
+    # and Tags" ).
+    commit_msg = api_request('differential.getcommitmessage', {
+        'revision_id': revision_id})
+    commit_msg = '\n'.join(
+        s for s in commit_msg.splitlines() if not should_strip_line(s))
+
+    # Write diff to file.
+    diff_file, path = tempfile.mkstemp(prefix='phabdiff', text=True)
+    with open(path, 'wt') as diff_file:
+        diff_file.write(rawdiff)
+
+    print('Applying diff to working directory.')
+    with open(path, 'rt') as diff_file:
+        subprocess.check_call(['git', 'apply'], stdin=diff_file)
+    os.remove(path)
+
+    # Commit all changed files.
+    subprocess.check_call(['git', 'commit', '-a', '-m', commit_msg])
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    subparsers = parser.add_subparsers(
+        title='subcommands')
+
+    apply_parser = subparsers.add_parser(
+        'apply',
+        help='Fetch the latest diff for the given differential ID from '
+             'reviews.llvm.org and apply it to the working directory.')
+    apply_parser.add_argument('ID', help='Differential ID, e.g. D5678')
+    apply_parser.set_defaults(func=apply_patch)
+
+    args = parser.parse_args()
+    if not hasattr(args, 'func'):
+        parser.print_help()
+        print('llvm-patch: A subcommand is required')
+        sys.exit(1)
+
+    args.func(args)
+    print('WARNING: This script is work-in-progress. Double-check results \n'
+          '         before pushing changes!')
+
+
+if __name__ == "__main__":
+    main()