diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
index 98139c72..11cff90a 100644
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -50,6 +50,7 @@ phutil_register_library_map(array(
     'ArcanistEventType' => 'events/constant/ArcanistEventType.php',
     'ArcanistExportWorkflow' => 'workflow/ArcanistExportWorkflow.php',
     'ArcanistFilenameLinter' => 'lint/linter/ArcanistFilenameLinter.php',
+    'ArcanistFlagWorkflow' => 'workflow/ArcanistFlagWorkflow.php',
     'ArcanistGeneratedLinter' => 'lint/linter/ArcanistGeneratedLinter.php',
     'ArcanistGetConfigWorkflow' => 'workflow/ArcanistGetConfigWorkflow.php',
     'ArcanistGitAPI' => 'repository/api/ArcanistGitAPI.php',
@@ -168,6 +169,7 @@ phutil_register_library_map(array(
     'ArcanistEventType' => 'PhutilEventType',
     'ArcanistExportWorkflow' => 'ArcanistBaseWorkflow',
     'ArcanistFilenameLinter' => 'ArcanistLinter',
+    'ArcanistFlagWorkflow' => 'ArcanistBaseWorkflow',
     'ArcanistGeneratedLinter' => 'ArcanistLinter',
     'ArcanistGetConfigWorkflow' => 'ArcanistBaseWorkflow',
     'ArcanistGitAPI' => 'ArcanistRepositoryAPI',
diff --git a/src/workflow/ArcanistFlagWorkflow.php b/src/workflow/ArcanistFlagWorkflow.php
new file mode 100644
index 00000000..6e172ee8
--- /dev/null
+++ b/src/workflow/ArcanistFlagWorkflow.php
@@ -0,0 +1,231 @@
+<?php
+
+/*
+ * Copyright 2012 Facebook, Inc.
+ *
+ * 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.
+ */
+
+/**
+ * @group workflow
+ */
+final class ArcanistFlagWorkflow extends ArcanistBaseWorkflow {
+
+  private static $colorMap = array(
+    0 => 'red',     // Red
+    1 => 'yellow',  // Orange
+    2 => 'yellow',  // Yellow
+    3 => 'green',   // Green
+    4 => 'blue',    // Blue
+    5 => 'magenta', // Pink
+    6 => 'magenta', // Purple
+    7 => 'default', // Checkered
+  );
+
+  private static $colorSpec = array(
+    'red' => 0,       'r' => 0,   0 => 0,
+    'orange' => 1,    'o' => 1,   1 => 1,
+    'yellow' => 2,    'y' => 2,   2 => 2,
+    'green' => 3,     'g' => 3,   3 => 3,
+    'blue' => 4,      'b' => 4,   4 => 4,
+    'pink' => 5,      'p' => 5,   5 => 5,
+    'purple' => 6,    'v' => 6,   6 => 6,
+    'checkered' => 7, 'c' => 7,   7 => 7,
+  );
+
+  public function getCommandSynopses() {
+    return phutil_console_format(<<<EOTEXT
+      **flag** [__object__ ...]
+      **flag** __object__ --clear
+      **flag** __object__ [--edit] [--color __color__] [--note __note__]
+EOTEXT
+      );
+  }
+
+  public function getCommandHelp() {
+    return phutil_console_format(<<<EOTEXT
+          In the first form, list objects you've flagged. You can provide the
+          names of one or more objects (Maniphest tasks T#\##, Differential
+          revisions D###, Diffusion references rXXX???, or PHIDs PHID-XXX-???)
+          to print only flags for those objects.
+
+          In the second form, clear an existing flag on one object.
+
+          In the third form, create or update a flag on one object. Color
+          defaults to blue and note to empty, but if you omit both you must
+          pass --edit.
+EOTEXT
+      );
+  }
+
+  public function getArguments() {
+    return array(
+      '*' => 'objects',
+      'clear' => array(
+        'help' => 'Delete the flag on an object.'
+      ),
+      'edit' => array(
+        'help' => 'Edit the flag on an object.'
+      ),
+      'color' => array(
+        'param' => 'color',
+        'help' => 'Set the color of a flag.'
+      ),
+      'note' => array(
+        'param' => 'note',
+        'help' => 'Set the note on a flag.'
+      ),
+    );
+  }
+
+  public function requiresConduit() {
+    return true;
+  }
+
+  public function requiresAuthentication() {
+    return true;
+  }
+
+  private static function flagWasEdited($flag, $verb) {
+    $color = idx(self::$colorMap, $flag['color'], 'cyan');
+    $note = $flag['note'];
+    if ($note) {
+      // Make sure notes that are long or have line breaks in them or
+      // whatever don't mess up the formatting.
+      $note = implode(' ', preg_split('/\s+/', $note));
+      $note = ' ('.phutil_utf8_shorten($note, 40, '...').')';
+    }
+    echo phutil_console_format(
+      "<fg:{$color}>%s</fg> flag%s $verb!\n",
+      $flag['colorName'],
+      $note);
+  }
+
+  public function run() {
+    $conduit = $this->getConduit();
+    $objects = $this->getArgument('objects', array());
+    $phids = array();
+
+    $clear = $this->getArgument('clear');
+    $edit = $this->getArgument('edit');
+    // I don't trust PHP to distinguish 0 (red) from null.
+    $color = $this->getArgument('color', -1);
+    $note = $this->getArgument('note');
+    $editing = $edit || ($color != -1) || $note;
+
+    if ($editing && $clear) {
+      throw new ArcanistUsageException("You can't both edit and clear a flag.");
+    }
+    if (($editing || $clear) && count($objects) != 1) {
+      throw new ArcanistUsageException("Specify exactly one object.");
+    }
+
+    if (!empty($objects)) {
+      // First off, convert the passed objects to PHIDs.
+      $handles = $conduit->callMethodSynchronous(
+        'phid.lookup',
+        array(
+          'names' => $objects,
+        ));
+      foreach ($objects as $object) {
+        if (isset($handles[$object])) {
+          $phids[$object] = $handles[$object]['phid'];
+        } else {
+          echo phutil_console_format("**%s** doesn't exist.\n", $object);
+        }
+      }
+      if (empty($phids)) {
+        // flag.query treats an empty objectPHIDs parameter as "don't use this
+        // constraint". However, if the user gives a list of objects but none
+        // of them exist and have flags, we shouldn't dump the full list on
+        // them after telling them that. Conveniently, we already told them,
+        // so we can go quit now.
+        return 0;
+      }
+    }
+
+    if ($clear) {
+      // All right, we're going to clear a flag. First clear it. Then tell the
+      // user we cleared it. Step four: profit!
+      $flag = $conduit->callMethodSynchronous(
+        'flag.delete',
+        array(
+          'objectPHID' => head($phids),
+        ));
+      if (!$flag) {
+        echo phutil_console_format("**%s** has no flag to clear.\n", $object);
+      } else {
+        self::flagWasEdited($flag, 'deleted');
+      }
+    } elseif ($editing) {
+      // Let's set some flags. Just like Minesweeper, but less distracting.
+      $flag_params = array(
+        'objectPHID' => head($phids),
+      );
+      if (isset(self::$colorSpec[$color])) {
+        $flag_params['color'] = self::$colorSpec[strtolower($color)];
+      }
+      if ($note) {
+        $flag_params['note'] = $note;
+      }
+      $flag = $conduit->callMethodSynchronous(
+        'flag.edit',
+        $flag_params
+      );
+      self::flagWasEdited($flag, $flag['new'] ? 'created' : 'edited');
+    } else {
+      // Okay, list mode. Let's find the flags, which we didn't need to do
+      // otherwise because Conduit does it for us.
+      $flags = ipull(
+        $this->getConduit()->callMethodSynchronous(
+          'flag.query',
+          array(
+            'ownerPHIDs' => array($this->getUserPHID()),
+            'objectPHIDs' => array_values($phids),
+          )),
+        null,
+        'objectPHID');
+      foreach ($phids as $object => $phid) {
+        if (!isset($flags[$phid])) {
+          echo phutil_console_format("**%s** has no flag.\n", $object);
+        }
+      }
+
+      if (empty($flags)) {
+        // If the user passed no object names, then we should print the full
+        // list, but it's empty, so tell the user they have no flags.
+        // If the user passed object names, we already told them all their
+        // objects are nonexistent or unflagged.
+        if (empty($objects)) {
+          echo "You have no flagged objects.\n";
+        }
+      } else {
+        // Print ALL the flags. With fancy formatting. Because fancy formatting
+        // is _cool_.
+        $name_len = 1 + max(array_map('strlen', ipull($flags, 'colorName')));
+        foreach ($flags as $flag) {
+          $color = idx(self::$colorMap, $flag['color'], 'cyan');
+          echo phutil_console_format(
+            "[<fg:{$color}>%s</fg>] %s\n",
+            str_pad($flag['colorName'], $name_len),
+            $flag['handle']['fullname']);
+          if ($flag['note']) {
+            $note = phutil_console_wrap($flag['note'], $name_len + 3);
+            echo rtrim($note)."\n";
+          }
+        }
+      }
+    }
+  }
+
+}