diff --git a/gsi/gsi_util/Android.bp b/gsi/gsi_util/Android.bp
index 8ec481a35..2eb80fdf8 100644
--- a/gsi/gsi_util/Android.bp
+++ b/gsi/gsi_util/Android.bp
@@ -20,6 +20,9 @@ python_binary_host {
     "gsi_util/commands/*.py",
     "gsi_util/utils/*.py",
   ],
+  required: [
+    "avbtool",
+  ],
   version: {
     py2: {
       enabled: true,
diff --git a/gsi/gsi_util/gsi_util.py b/gsi/gsi_util/gsi_util.py
index d3cab52ff..2b535a85f 100755
--- a/gsi/gsi_util/gsi_util.py
+++ b/gsi/gsi_util/gsi_util.py
@@ -28,7 +28,7 @@ class GsiUtil(object):
 
   # Adds gsi_util COMMAND here.
   # TODO(bowgotsai): auto collect from gsi_util/commands/*.py
-  _COMMANDS = ['hello']
+  _COMMANDS = ['flash_gsi', 'hello']
 
   _LOGGING_FORMAT = '%(message)s'
   _LOGGING_LEVEL = logging.WARNING
diff --git a/gsi/gsi_util/gsi_util/commands/flash_gsi.py b/gsi/gsi_util/gsi_util/commands/flash_gsi.py
new file mode 100644
index 000000000..6f8fd9dfe
--- /dev/null
+++ b/gsi/gsi_util/gsi_util/commands/flash_gsi.py
@@ -0,0 +1,63 @@
+# Copyright 2017 - The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Implementation of gsi_util flash_gsi command."""
+
+from gsi_util.utils import cmd_utils
+from gsi_util.utils import fastboot_utils
+from gsi_util.utils import file_utils
+
+
+def do_flash_gsi(args):
+  """Flashes a GSI image (system.img).
+
+  Also erases userdata/metadata partition and disables
+  Android Verified Boot (AVB).
+
+  Args:
+    args: flash_gsi command arguments.
+  """
+
+  fastboot_utils.erase()  # erases userdata/cache partition
+  # Not every device has metadata partition, so allow_error is True.
+  fastboot_utils.erase('metadata', allow_error=True)
+
+  # Flashes GSI.
+  fastboot_utils.flash('system', args.image)
+
+  # Disables AVB.
+  with file_utils.UnopenedTemporaryFile() as vbmeta_image:
+    # vbmeta flag 2 means disable entire AVB verification.
+    cmd_utils.run_command(['avbtool', 'make_vbmeta_image',
+                           '--flag', '2',
+                           '--padding_size', '4096',
+                           '--output', vbmeta_image])
+    # Not every device uses AVB, so allow_error is True.
+    fastboot_utils.flash('vbmeta', vbmeta_image, allow_error=True)
+
+  # Reboots the device.
+  fastboot_utils.reboot()
+
+
+def setup_command_args(subparsers):
+  """Sets up command args for 'flash_gsi'."""
+  parser = subparsers.add_parser(
+      'flash_gsi', help='flash a GSI image',
+      description=('Flash a GSI image - '
+                   'including erasing userdata, '
+                   'disabling AVB (if the device supports AVB) '
+                   'and erasing metadata partition (if the device has).'))
+  parser.add_argument('-i', '--image',
+                      help='the GSI image to flash', type=str)
+  parser.set_defaults(func=do_flash_gsi)
diff --git a/gsi/gsi_util/gsi_util/utils/fastboot_utils.py b/gsi/gsi_util/gsi_util/utils/fastboot_utils.py
new file mode 100644
index 000000000..a6f11eecd
--- /dev/null
+++ b/gsi/gsi_util/gsi_util/utils/fastboot_utils.py
@@ -0,0 +1,45 @@
+# Copyright 2017 - The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Fastboot-related commands."""
+
+from gsi_util.utils.cmd_utils import run_command
+
+
+def flash(partition_name, image_name=None, allow_error=False):
+  """fastboot flash a partition with a given image."""
+
+  cmd = ['fastboot', 'flash', partition_name]
+
+  # image_name can be None, for `fastboot` to flash
+  # ${ANDROID_PRODUCT_OUT}/{partition_name}.img.
+  if image_name is not None:
+    cmd.append(image_name)
+
+  run_command(cmd, raise_on_error=not allow_error)
+
+
+def erase(partition_name=None, allow_error=False):
+  """fastboot erase a partition."""
+
+  if partition_name is None:
+    run_command(['fastboot', '-w'], raise_on_error=not allow_error)
+  else:
+    run_command(['fastboot', 'erase', partition_name],
+                raise_on_error=not allow_error)
+
+
+def reboot():
+  """fastboot reboot a device."""
+  run_command(['fastboot', 'reboot'], raise_on_error=False)