diff --git a/tools_webrtc/mb/docs/design_spec.md b/tools_webrtc/mb/docs/design_spec.md
index 33fda80..0aaaf89 100644
--- a/tools_webrtc/mb/docs/design_spec.md
+++ b/tools_webrtc/mb/docs/design_spec.md
@@ -52,8 +52,8 @@
 args`) to use.
 
 A config can either be specified directly (useful for testing) or by specifying
-the master name and builder name (useful on the bots so that they do not need
-to specify a config directly and can be hidden from the details).
+the builder group name and builder name (useful on the bots so that they do not
+need to specify a config directly and can be hidden from the details).
 
 See the [user guide](user_guide.md#mb_config.pyl) for details.
 
diff --git a/tools_webrtc/mb/docs/user_guide.md b/tools_webrtc/mb/docs/user_guide.md
index 9817553..8c66cd3 100644
--- a/tools_webrtc/mb/docs/user_guide.md
+++ b/tools_webrtc/mb/docs/user_guide.md
@@ -27,8 +27,8 @@
 mb analyze -c chromium_linux_rel //out/Release input.json output.json
 ```
 
-Either the `-c/--config` flag or the `-m/--master` and `-b/--builder` flags
-must be specified so that `mb` can figure out which config to use.
+Either the `-c/--config` flag or the `-m/--builder-group` and `-b/--builder`
+flags must be specified so that `mb` can figure out which config to use.
 
 The first positional argument must be a GN-style "source-absolute" path
 to the build directory.
@@ -90,15 +90,16 @@
 `build_targets` differ from each other or from `compile_targets` and
 `test_targets`.
 
-The `-b/--builder`, `-c/--config`, `-f/--config-file`, `-m/--master`,
+The `-b/--builder`, `-c/--config`, `-f/--config-file`, `-m/--builder-group`,
 `-q/--quiet`, and `-v/--verbose` flags work as documented for `mb gen`.
 
 ### `mb audit`
 
 `mb audit` is used to track the progress of the GYP->GN migration. You can
-use it to check a single master, or all the masters we care about. See
-`mb help audit` for more details (most people are not expected to care about
-this).
+use it to check a single builder group, or all the builder groups we care
+about.
+See `mb help audit` for more details (most people are not expected to care
+about this).
 
 ### `mb gen`
 
@@ -111,8 +112,8 @@
 % mb gen -c linux_rel_trybot //out/Release
 ```
 
-Either the `-c/--config` flag or the `-m/--master` and `-b/--builder` flags
-must be specified so that `mb` can figure out which config to use. The
+Either the `-c/--config` flag or the `-m/--builder-group` and `-b/--builder`
+flags must be specified so that `mb` can figure out which config to use. The
 `--phase` flag must also be used with builders that have multiple
 build/compile steps (and only with those builders).
 
@@ -149,7 +150,7 @@
 Prints what command will be run by `mb gen` (like `mb gen -n` but does
 not require you to specify a path).
 
-The `-b/--builder`, `-c/--config`, `-f/--config-file`, `-m/--master`,
+The `-b/--builder`, `-c/--config`, `-f/--config-file`, `-m/--builder-group`,
 `--phase`, `-q/--quiet`, and `-v/--verbose` flags work as documented for
 `mb gen`.
 
@@ -198,11 +199,11 @@
 having to juggle long lists of GYP_DEFINES and gn args by hand.
 
 `mb_config.pyl` is structured as a file containing a single PYthon Literal
-expression: a dictionary with three main keys, `masters`, `configs` and
+expression: a dictionary with three main keys, `builder_groups`, `configs` and
 `mixins`.
 
-The `masters` key contains a nested series of dicts containing mappings
-of master -> builder -> config . This allows us to isolate the buildbot
+The `builder_groups` key contains a nested series of dicts containing mappings
+of builder group -> builder -> config . This allows us to isolate the buildbot
 recipes from the actual details of the configs. The config should either
 be a single string value representing a key in the `configs` dictionary,
 or a list of strings, each of which is a key in the `configs` dictionary;
diff --git a/tools_webrtc/mb/mb.py b/tools_webrtc/mb/mb.py
index 67d25d0..358a66e 100755
--- a/tools_webrtc/mb/mb.py
+++ b/tools_webrtc/mb/mb.py
@@ -54,7 +54,7 @@
     self.sep = os.sep
     self.args = argparse.Namespace()
     self.configs = {}
-    self.masters = {}
+    self.builder_groups = {}
     self.mixins = {}
     self.isolate_exe = 'isolate.exe' if self.platform.startswith(
         'win') else 'isolate'
@@ -80,8 +80,10 @@
     def AddCommonOptions(subp):
       subp.add_argument('-b', '--builder',
                         help='builder name to look up config from')
-      subp.add_argument('-m', '--master',
-                        help='master name to look up config from')
+      subp.add_argument('-m', '--builder-group',
+                        # TODO(crbug.com/1117773): Remove the 'master' args.
+                        '--master',
+                        help='builder group name to look up config from')
       subp.add_argument('-c', '--config',
                         help='configuration to analyze')
       subp.add_argument('--phase',
@@ -252,10 +254,10 @@
   def CmdExport(self):
     self.ReadConfigFile()
     obj = {}
-    for master, builders in self.masters.items():
-      obj[master] = {}
+    for builder_group, builders in self.builder_groups.items():
+      obj[builder_group] = {}
       for builder in builders:
-        config = self.masters[master][builder]
+        config = self.builder_groups[builder_group][builder]
         if not config:
           continue
 
@@ -269,7 +271,7 @@
           if 'error' in args:
             continue
 
-        obj[master][builder] = args
+        obj[builder_group][builder] = args
 
     # Dump object and trim trailing whitespace.
     s = '\n'.join(l.rstrip() for l in
@@ -402,13 +404,13 @@
 
     # Build a list of all of the configs referenced by builders.
     all_configs = {}
-    for master in self.masters:
-      for config in self.masters[master].values():
+    for builder_group in self.builder_groups:
+      for config in self.builder_groups[builder_group].values():
         if isinstance(config, dict):
           for c in config.values():
-            all_configs[c] = master
+            all_configs[c] = builder_group
         else:
-          all_configs[config] = master
+          all_configs[config] = builder_group
 
     # Check that every referenced args file or config actually exists.
     for config, loc in all_configs.items():
@@ -459,7 +461,7 @@
     build_dir = self.args.path[0]
 
     vals = self.DefaultVals()
-    if self.args.builder or self.args.master or self.args.config:
+    if self.args.builder or self.args.builder_group or self.args.config:
       vals = self.Lookup()
       # Re-run gn gen in order to ensure the config is consistent with the
       # build dir.
@@ -517,7 +519,7 @@
                  (self.args.config_file, e))
 
     self.configs = contents['configs']
-    self.masters = contents['masters']
+    self.builder_groups = contents['builder_groups']
     self.mixins = contents['mixins']
 
   def ReadIsolateMap(self):
@@ -532,38 +534,39 @@
 
   def ConfigFromArgs(self):
     if self.args.config:
-      if self.args.master or self.args.builder:
-        raise MBErr('Can not specific both -c/--config and -m/--master or '
-                    '-b/--builder')
+      if self.args.builder_group or self.args.builder:
+        raise MBErr('Can not specific both -c/--config and -m/--builder-group '
+                    'or -b/--builder')
 
       return self.args.config
 
-    if not self.args.master or not self.args.builder:
+    if not self.args.builder_group or not self.args.builder:
       raise MBErr('Must specify either -c/--config or '
-                  '(-m/--master and -b/--builder)')
+                  '(-m/--builder-group and -b/--builder)')
 
-    if not self.args.master in self.masters:
+    if not self.args.builder_group in self.builder_groups:
       raise MBErr('Master name "%s" not found in "%s"' %
-                  (self.args.master, self.args.config_file))
+                  (self.args.builder_group, self.args.config_file))
 
-    if not self.args.builder in self.masters[self.args.master]:
-      raise MBErr('Builder name "%s"  not found under masters[%s] in "%s"' %
-                  (self.args.builder, self.args.master, self.args.config_file))
+    if not self.args.builder in self.builder_groups[self.args.builder_group]:
+      raise MBErr(
+          'Builder name "%s"  not found under builder_groups[%s] in "%s"' %
+          (self.args.builder, self.args.builder_group, self.args.config_file))
 
-    config = self.masters[self.args.master][self.args.builder]
+    config = self.builder_groups[self.args.builder_group][self.args.builder]
     if isinstance(config, dict):
       if self.args.phase is None:
         raise MBErr('Must specify a build --phase for %s on %s' %
-                    (self.args.builder, self.args.master))
+                    (self.args.builder, self.args.builder_group))
       phase = str(self.args.phase)
       if phase not in config:
         raise MBErr('Phase %s doesn\'t exist for %s on %s' %
-                    (phase, self.args.builder, self.args.master))
+                    (phase, self.args.builder, self.args.builder_group))
       return config[phase]
 
     if self.args.phase is not None:
       raise MBErr('Must not specify a build --phase for %s on %s' %
-                  (self.args.builder, self.args.master))
+                  (self.args.builder, self.args.builder_group))
     return config
 
   def FlattenConfig(self, config):
diff --git a/tools_webrtc/mb/mb_config.pyl b/tools_webrtc/mb/mb_config.pyl
index 4519e8f..4bb04aa 100644
--- a/tools_webrtc/mb/mb_config.pyl
+++ b/tools_webrtc/mb/mb_config.pyl
@@ -12,12 +12,12 @@
 # easy to try different configurations of GN args in tryjob patches.
 
 {
-  # This is a map of buildbot master names -> buildbot builder names ->
+  # This is a map of buildbot builder group names -> buildbot builder names ->
   # config names (where each config name is a key in the 'configs' dict,
   # above). mb uses this dict to look up which config to use for a given bot.
   # The builders should be sorted by the order they appear in the /builders
   # page on the buildbots, *not* alphabetically.
-  'masters': {
+  'builder_groups': {
     'client.webrtc': {
       # iOS
       'iOS32 Debug': 'ios_debug_bot_arm',
diff --git a/tools_webrtc/mb/mb_unittest.py b/tools_webrtc/mb/mb_unittest.py
index 0cf93bb..eb11d09 100755
--- a/tools_webrtc/mb/mb_unittest.py
+++ b/tools_webrtc/mb/mb_unittest.py
@@ -111,12 +111,12 @@
 
 TEST_CONFIG = """\
 {
-  'masters': {
+  'builder_groups': {
     'chromium': {},
-    'fake_master': {
+    'fake_group': {
       'fake_builder': 'rel_bot',
       'fake_debug_builder': 'debug_goma',
-      'fake_args_bot': '//build/args/bots/fake_master/fake_args_bot.gn',
+      'fake_args_bot': '//build/args/bots/fake_group/fake_args_bot.gn',
       'fake_multi_phase': { 'phase_1': 'phase_1', 'phase_2': 'phase_2'},
       'fake_android_bot': 'android_bot',
     },
@@ -169,7 +169,7 @@
         },
       }''')
     mbw.files.setdefault(
-        mbw.ToAbsPath('//build/args/bots/fake_master/fake_args_bot.gn'),
+        mbw.ToAbsPath('//build/args/bots/fake_group/fake_args_bot.gn'),
         'is_debug = false\n')
     if files:
       for path, contents in files.items():
@@ -238,12 +238,12 @@
                   '--check\n', mbw.out)
 
     mbw = self.fake_mbw()
-    self.check(['gen', '-m', 'fake_master', '-b', 'fake_args_bot',
+    self.check(['gen', '-m', 'fake_group', '-b', 'fake_args_bot',
                 '//out/Debug'],
                mbw=mbw, ret=0)
     self.assertEqual(
         mbw.files['/fake_src/out/Debug/args.gn'],
-        'import("//build/args/bots/fake_master/fake_args_bot.gn")\n\n')
+        'import("//build/args/bots/fake_group/fake_args_bot.gn")\n\n')
 
 
   def test_gen_fails(self):
@@ -801,26 +801,26 @@
 
   def test_multiple_phases(self):
     # Check that not passing a --phase to a multi-phase builder fails.
-    mbw = self.check(['lookup', '-m', 'fake_master', '-b', 'fake_multi_phase'],
+    mbw = self.check(['lookup', '-m', 'fake_group', '-b', 'fake_multi_phase'],
                      ret=1)
     self.assertIn('Must specify a build --phase', mbw.out)
 
     # Check that passing a --phase to a single-phase builder fails.
-    mbw = self.check(['lookup', '-m', 'fake_master', '-b', 'fake_builder',
+    mbw = self.check(['lookup', '-m', 'fake_group', '-b', 'fake_builder',
                       '--phase', 'phase_1'], ret=1)
     self.assertIn('Must not specify a build --phase', mbw.out)
 
     # Check that passing a wrong phase key to a multi-phase builder fails.
-    mbw = self.check(['lookup', '-m', 'fake_master', '-b', 'fake_multi_phase',
+    mbw = self.check(['lookup', '-m', 'fake_group', '-b', 'fake_multi_phase',
                       '--phase', 'wrong_phase'], ret=1)
     self.assertIn('Phase wrong_phase doesn\'t exist', mbw.out)
 
     # Check that passing a correct phase key to a multi-phase builder passes.
-    mbw = self.check(['lookup', '-m', 'fake_master', '-b', 'fake_multi_phase',
+    mbw = self.check(['lookup', '-m', 'fake_group', '-b', 'fake_multi_phase',
                       '--phase', 'phase_1'], ret=0)
     self.assertIn('phase = 1', mbw.out)
 
-    mbw = self.check(['lookup', '-m', 'fake_master', '-b', 'fake_multi_phase',
+    mbw = self.check(['lookup', '-m', 'fake_group', '-b', 'fake_multi_phase',
                       '--phase', 'phase_2'], ret=0)
     self.assertIn('phase = 2', mbw.out)