diff --git a/git_command.py b/git_command.py
index 54db4d16..f5352ea0 100644
--- a/git_command.py
+++ b/git_command.py
@@ -98,13 +98,15 @@ class _GitCall(object):
     return fun
 git = _GitCall()
 
-def git_require(min_version, fail=False):
+def git_require(min_version, fail=False, msg=''):
   git_version = git.version_tuple()
   if min_version <= git_version:
     return True
   if fail:
     need = '.'.join(map(str, min_version))
-    print('fatal: git %s or later required' % need, file=sys.stderr)
+    if msg:
+      msg = ' for ' + msg
+    print('fatal: git %s or later required%s' % (need, msg), file=sys.stderr)
     sys.exit(1)
   return False
 
diff --git a/manifest_xml.py b/manifest_xml.py
index 94d22b3c..3814a25a 100644
--- a/manifest_xml.py
+++ b/manifest_xml.py
@@ -413,6 +413,12 @@ class XmlManifest(object):
     self._Load()
     return self._manifest_server
 
+  @property
+  def CloneFilter(self):
+    if self.manifestProject.config.GetBoolean('repo.partialclone'):
+      return self.manifestProject.config.GetString('repo.clonefilter')
+    return None
+
   @property
   def IsMirror(self):
     return self.manifestProject.config.GetBoolean('repo.mirror')
diff --git a/project.py b/project.py
index 67d3bb20..9702e9da 100755
--- a/project.py
+++ b/project.py
@@ -1226,7 +1226,8 @@ class Project(object):
                        archive=False,
                        optimized_fetch=False,
                        prune=False,
-                       submodules=False):
+                       submodules=False,
+                       clone_filter=None):
     """Perform only the network IO portion of the sync process.
        Local working directory/branch state is not affected.
     """
@@ -1309,7 +1310,8 @@ class Project(object):
         not self._RemoteFetch(initial=is_new, quiet=quiet, alt_dir=alt_dir,
                               current_branch_only=current_branch_only,
                               no_tags=no_tags, prune=prune, depth=depth,
-                              submodules=submodules, force_sync=force_sync)):
+                              submodules=submodules, force_sync=force_sync,
+                              clone_filter=clone_filter)):
       return False
 
     mp = self.manifest.manifestProject
@@ -1959,7 +1961,8 @@ class Project(object):
                    prune=False,
                    depth=None,
                    submodules=False,
-                   force_sync=False):
+                   force_sync=False,
+                   clone_filter=None):
 
     is_sha1 = False
     tag_name = None
@@ -2050,6 +2053,11 @@ class Project(object):
 
     cmd = ['fetch']
 
+    if clone_filter:
+      git_require((2, 19, 0), fail=True, msg='partial clones')
+      cmd.append('--filter=%s' % clone_filter)
+      self.config.SetString('extensions.partialclone', self.remote.name)
+
     if depth:
       cmd.append('--depth=%s' % depth)
     else:
@@ -2150,12 +2158,12 @@ class Project(object):
           return self._RemoteFetch(name=name,
                                    current_branch_only=current_branch_only,
                                    initial=False, quiet=quiet, alt_dir=alt_dir,
-                                   depth=None)
+                                   depth=None, clone_filter=clone_filter)
         else:
           # Avoid infinite recursion: sync all branches with depth set to None
           return self._RemoteFetch(name=name, current_branch_only=False,
                                    initial=False, quiet=quiet, alt_dir=alt_dir,
-                                   depth=None)
+                                   depth=None, clone_filter=clone_filter)
 
     return ok
 
diff --git a/repo b/repo
index 8ed147df..649c4e48 100755
--- a/repo
+++ b/repo
@@ -199,6 +199,13 @@ group.add_option('--dissociate',
 group.add_option('--depth', type='int', default=None,
                  dest='depth',
                  help='create a shallow clone with given depth; see git clone')
+group.add_option('--partial-clone', action='store_true',
+                 dest='partial_clone',
+                 help='perform partial clone (https://git-scm.com/'
+                 'docs/gitrepository-layout#_code_partialclone_code)')
+group.add_option('--clone-filter', action='store', default='blob:none',
+                 dest='clone_filter',
+                 help='filter for use with --partial-clone [default: %default]')
 group.add_option('--archive',
                  dest='archive', action='store_true',
                  help='checkout an archive instead of a git repository for '
diff --git a/subcmds/init.py b/subcmds/init.py
index 1c809ab4..eaa6da50 100644
--- a/subcmds/init.py
+++ b/subcmds/init.py
@@ -115,6 +115,13 @@ to update the working directory files.
     g.add_option('--depth', type='int', default=None,
                  dest='depth',
                  help='create a shallow clone with given depth; see git clone')
+    g.add_option('--partial-clone', action='store_true',
+                 dest='partial_clone',
+                 help='perform partial clone (https://git-scm.com/'
+                 'docs/gitrepository-layout#_code_partialclone_code)')
+    g.add_option('--clone-filter', action='store', default='blob:none',
+                 dest='clone_filter',
+                 help='filter for use with --partial-clone [default: %default]')
     g.add_option('--archive',
                  dest='archive', action='store_true',
                  help='checkout an archive instead of a git repository for '
@@ -253,13 +260,25 @@ to update the working directory files.
               'in another location.', file=sys.stderr)
         sys.exit(1)
 
+    if opt.partial_clone:
+      if opt.mirror:
+        print('fatal: --mirror and --partial-clone are mutually exclusive',
+              file=sys.stderr)
+        sys.exit(1)
+      m.config.SetString('repo.partialclone', 'true')
+      if opt.clone_filter:
+        m.config.SetString('repo.clonefilter', opt.clone_filter)
+    else:
+      opt.clone_filter = None
+
     if opt.submodules:
       m.config.SetString('repo.submodules', 'true')
 
     if not m.Sync_NetworkHalf(is_new=is_new, quiet=opt.quiet,
         clone_bundle=not opt.no_clone_bundle,
         current_branch_only=opt.current_branch_only,
-        no_tags=opt.no_tags, submodules=opt.submodules):
+        no_tags=opt.no_tags, submodules=opt.submodules,
+        clone_filter=opt.clone_filter):
       r = m.GetRemote(m.remote.name)
       print('fatal: cannot obtain manifest %s' % r.url, file=sys.stderr)
 
diff --git a/subcmds/sync.py b/subcmds/sync.py
index 02cd3879..b752cfbe 100644
--- a/subcmds/sync.py
+++ b/subcmds/sync.py
@@ -85,6 +85,9 @@ class _FetchError(Exception):
   """Internal error thrown in _FetchHelper() when we don't want stack trace."""
   pass
 
+class _CheckoutError(Exception):
+  """Internal error thrown in _CheckoutOne() when we don't want stack trace."""
+
 class Sync(Command, MirrorSafeCommand):
   jobs = 1
   common = True
@@ -266,7 +269,7 @@ later is required to fix a server side protocol bug.
                  help=SUPPRESS_HELP)
 
   def _FetchProjectList(self, opt, projects, sem, *args, **kwargs):
-    """Main function of the fetch threads when jobs are > 1.
+    """Main function of the fetch threads.
 
     Delegates most of the work to _FetchHelper.
 
@@ -286,7 +289,8 @@ later is required to fix a server side protocol bug.
     finally:
         sem.release()
 
-  def _FetchHelper(self, opt, project, lock, fetched, pm, err_event):
+  def _FetchHelper(self, opt, project, lock, fetched, pm, err_event,
+                   clone_filter):
     """Fetch git objects for a single project.
 
     Args:
@@ -300,6 +304,7 @@ later is required to fix a server side protocol bug.
           lock held).
       err_event: We'll set this event in the case of an error (after printing
           out info about the error).
+      clone_filter: Filter for use in a partial clone.
 
     Returns:
       Whether the fetch was successful.
@@ -312,7 +317,6 @@ later is required to fix a server side protocol bug.
 
     # Encapsulate everything in a try/except/finally so that:
     # - We always set err_event in the case of an exception.
-    # - We always make sure we call sem.release().
     # - We always make sure we unlock the lock if we locked it.
     start = time.time()
     success = False
@@ -325,7 +329,8 @@ later is required to fix a server side protocol bug.
           clone_bundle=not opt.no_clone_bundle,
           no_tags=opt.no_tags, archive=self.manifest.IsArchive,
           optimized_fetch=opt.optimized_fetch,
-          prune=opt.prune)
+          prune=opt.prune,
+          clone_filter=clone_filter)
         self._fetch_times.Set(project, time.time() - start)
 
         # Lock around all the rest of the code, since printing, updating a set
@@ -389,7 +394,8 @@ later is required to fix a server side protocol bug.
                     lock=lock,
                     fetched=fetched,
                     pm=pm,
-                    err_event=err_event)
+                    err_event=err_event,
+                    clone_filter=self.manifest.CloneFilter)
       if self.jobs > 1:
         t = _threading.Thread(target = self._FetchProjectList,
                               kwargs = kwargs)
@@ -416,6 +422,148 @@ later is required to fix a server side protocol bug.
 
     return fetched
 
+  def _CheckoutWorker(self, opt, sem, project, *args, **kwargs):
+    """Main function of the fetch threads.
+
+    Delegates most of the work to _CheckoutOne.
+
+    Args:
+      opt: Program options returned from optparse.  See _Options().
+      projects: Projects to fetch.
+      sem: We'll release() this semaphore when we exit so that another thread
+          can be started up.
+      *args, **kwargs: Remaining arguments to pass to _CheckoutOne. See the
+          _CheckoutOne docstring for details.
+    """
+    try:
+      success = self._CheckoutOne(opt, project, *args, **kwargs)
+      if not success:
+        sys.exit(1)
+    finally:
+      sem.release()
+
+  def _CheckoutOne(self, opt, project, lock, pm, err_event):
+    """Checkout work tree for one project
+
+    Args:
+      opt: Program options returned from optparse.  See _Options().
+      project: Project object for the project to checkout.
+      lock: Lock for accessing objects that are shared amongst multiple
+          _CheckoutWorker() threads.
+      pm: Instance of a Project object.  We will call pm.update() (with our
+          lock held).
+      err_event: We'll set this event in the case of an error (after printing
+          out info about the error).
+
+    Returns:
+      Whether the fetch was successful.
+    """
+    # We'll set to true once we've locked the lock.
+    did_lock = False
+
+    if not opt.quiet:
+      print('Checking out project %s' % project.name)
+
+    # Encapsulate everything in a try/except/finally so that:
+    # - We always set err_event in the case of an exception.
+    # - We always make sure we unlock the lock if we locked it.
+    start = time.time()
+    syncbuf = SyncBuffer(self.manifest.manifestProject.config,
+                         detach_head=opt.detach_head)
+    success = False
+    try:
+      try:
+        project.Sync_LocalHalf(syncbuf, force_sync=opt.force_sync)
+        success = syncbuf.Finish()
+
+        # Lock around all the rest of the code, since printing, updating a set
+        # and Progress.update() are not thread safe.
+        lock.acquire()
+        did_lock = True
+
+        if not success:
+          err_event.set()
+          print('error: Cannot checkout %s' % (project.name),
+                file=sys.stderr)
+          raise _CheckoutError()
+
+        pm.update()
+      except _CheckoutError:
+        pass
+      except Exception as e:
+        print('error: Cannot checkout %s: %s: %s' %
+              (project.name, type(e).__name__, str(e)),
+              file=sys.stderr)
+        err_event.set()
+        raise
+    finally:
+      if did_lock:
+        lock.release()
+      finish = time.time()
+      self.event_log.AddSync(project, event_log.TASK_SYNC_LOCAL,
+                             start, finish, success)
+
+    return success
+
+  def _Checkout(self, all_projects, opt):
+    """Checkout projects listed in all_projects
+
+    Args:
+      all_projects: List of all projects that should be checked out.
+      opt: Program options returned from optparse.  See _Options().
+    """
+
+    # Perform checkouts in multiple threads when we are using partial clone.
+    # Without partial clone, all needed git objects are already downloaded,
+    # in this situation it's better to use only one process because the checkout
+    # would be mostly disk I/O; with partial clone, the objects are only
+    # downloaded when demanded (at checkout time), which is similar to the
+    # Sync_NetworkHalf case and parallelism would be helpful.
+    if self.manifest.CloneFilter:
+      syncjobs = self.jobs
+    else:
+      syncjobs = 1
+
+    lock = _threading.Lock()
+    pm = Progress('Syncing work tree', len(all_projects))
+
+    threads = set()
+    sem = _threading.Semaphore(syncjobs)
+    err_event = _threading.Event()
+
+    for project in all_projects:
+      # Check for any errors before running any more tasks.
+      # ...we'll let existing threads finish, though.
+      if err_event.isSet() and not opt.force_broken:
+        break
+
+      sem.acquire()
+      if project.worktree:
+        kwargs = dict(opt=opt,
+                      sem=sem,
+                      project=project,
+                      lock=lock,
+                      pm=pm,
+                      err_event=err_event)
+        if syncjobs > 1:
+          t = _threading.Thread(target=self._CheckoutWorker,
+                                kwargs=kwargs)
+          # Ensure that Ctrl-C will not freeze the repo process.
+          t.daemon = True
+          threads.add(t)
+          t.start()
+        else:
+          self._CheckoutWorker(**kwargs)
+
+    for t in threads:
+      t.join()
+
+    pm.end()
+    # If we saw an error, exit with code 1 so that other scripts can check.
+    if err_event.isSet():
+      print('\nerror: Exited sync due to checkout errors', file=sys.stderr)
+      sys.exit(1)
+
   def _GCProjects(self, projects):
     gc_gitdirs = {}
     for project in projects:
@@ -746,7 +894,8 @@ later is required to fix a server side protocol bug.
                                     current_branch_only=opt.current_branch_only,
                                     no_tags=opt.no_tags,
                                     optimized_fetch=opt.optimized_fetch,
-                                    submodules=self.manifest.HasSubmodules)
+                                    submodules=self.manifest.HasSubmodules,
+                                    clone_filter=self.manifest.CloneFilter)
       finish = time.time()
       self.event_log.AddSync(mp, event_log.TASK_SYNC_NETWORK,
                              start, finish, success)
@@ -846,20 +995,7 @@ later is required to fix a server side protocol bug.
     if self.UpdateProjectList(opt):
       sys.exit(1)
 
-    syncbuf = SyncBuffer(mp.config,
-                         detach_head = opt.detach_head)
-    pm = Progress('Syncing work tree', len(all_projects))
-    for project in all_projects:
-      pm.update()
-      if project.worktree:
-        start = time.time()
-        project.Sync_LocalHalf(syncbuf, force_sync=opt.force_sync)
-        self.event_log.AddSync(project, event_log.TASK_SYNC_LOCAL,
-                               start, time.time(), syncbuf.Recently())
-    pm.end()
-    print(file=sys.stderr)
-    if not syncbuf.Finish():
-      sys.exit(1)
+    self._Checkout(all_projects, opt)
 
     # If there's a notice that's supposed to print at the end of the sync, print
     # it now...