diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -363,6 +363,8 @@
     'PhutilSimpleOptionsLexerTestCase' => 'lexer/__tests__/PhutilSimpleOptionsLexerTestCase.php',
     'PhutilSimpleOptionsTestCase' => 'parser/__tests__/PhutilSimpleOptionsTestCase.php',
     'PhutilSimplifiedChineseLocale' => 'internationalization/locales/PhutilSimplifiedChineseLocale.php',
+    'PhutilSlackAuthAdapter' => 'auth/PhutilSlackAuthAdapter.php',
+    'PhutilSlackFuture' => 'future/slack/PhutilSlackFuture.php',
     'PhutilSocketChannel' => 'channel/PhutilSocketChannel.php',
     'PhutilSortVector' => 'utils/PhutilSortVector.php',
     'PhutilSpanishSpainLocale' => 'internationalization/locales/PhutilSpanishSpainLocale.php',
@@ -933,6 +935,8 @@
     'PhutilSimpleOptionsLexerTestCase' => 'PhutilTestCase',
     'PhutilSimpleOptionsTestCase' => 'PhutilTestCase',
     'PhutilSimplifiedChineseLocale' => 'PhutilLocale',
+    'PhutilSlackAuthAdapter' => 'PhutilOAuthAuthAdapter',
+    'PhutilSlackFuture' => 'FutureProxy',
     'PhutilSocketChannel' => 'PhutilChannel',
     'PhutilSortVector' => 'Phobject',
     'PhutilSpanishSpainLocale' => 'PhutilLocale',
diff --git a/src/auth/PhutilSlackAuthAdapter.php b/src/auth/PhutilSlackAuthAdapter.php
new file mode 100644
--- /dev/null
+++ b/src/auth/PhutilSlackAuthAdapter.php
@@ -0,0 +1,61 @@
+<?php
+
+/**
+ * Authentication adapter for Slack OAuth2.
+ */
+final class PhutilSlackAuthAdapter extends PhutilOAuthAuthAdapter {
+
+  public function getAdapterType() {
+    return 'Slack';
+  }
+
+  public function getAdapterDomain() {
+    return 'slack.com';
+  }
+
+  public function getAccountID() {
+    $user = $this->getOAuthAccountData('user');
+    return idx($user, 'id');
+  }
+
+  public function getAccountEmail() {
+    $user = $this->getOAuthAccountData('user');
+    return idx($user, 'email');
+  }
+
+  public function getAccountImageURI() {
+    $user = $this->getOAuthAccountData('user');
+    return idx($user, 'image_512');
+  }
+
+  public function getAccountRealName() {
+    $user = $this->getOAuthAccountData('user');
+    return idx($user, 'name');
+  }
+
+  protected function getAuthenticateBaseURI() {
+    return 'https://slack.com/oauth/authorize';
+  }
+
+  protected function getTokenBaseURI() {
+    return 'https://slack.com/api/oauth.access';
+  }
+
+  public function getScope() {
+    return 'identity.basic,identity.team,identity.avatar';
+  }
+
+  public function getExtraAuthenticateParameters() {
+    return array(
+      'response_type' => 'code',
+    );
+  }
+
+  protected function loadOAuthAccountData() {
+    return id(new PhutilSlackFuture())
+      ->setAccessToken($this->getAccessToken())
+      ->setRawSlackQuery('users.identity')
+      ->resolve();
+  }
+
+}
diff --git a/src/future/slack/PhutilSlackFuture.php b/src/future/slack/PhutilSlackFuture.php
new file mode 100644
--- /dev/null
+++ b/src/future/slack/PhutilSlackFuture.php
@@ -0,0 +1,87 @@
+<?php
+
+final class PhutilSlackFuture extends FutureProxy {
+
+  private $future;
+  private $clientID;
+  private $accessToken;
+  private $action;
+  private $params;
+  private $method = 'GET';
+
+  public function __construct() {
+    parent::__construct(null);
+  }
+
+  public function setAccessToken($token) {
+    $this->accessToken = $token;
+    return $this;
+  }
+
+  public function setClientID($client_id) {
+    $this->clientID = $client_id;
+    return $this;
+  }
+
+  public function setRawSlackQuery($action, array $params = array()) {
+    $this->action = $action;
+    $this->params = $params;
+    return $this;
+  }
+
+  public function setMethod($method) {
+    $this->method = $method;
+    return $this;
+  }
+
+  protected function getProxiedFuture() {
+    if (!$this->future) {
+      $params = $this->params;
+
+      if (!$this->action) {
+        throw new Exception(pht('You must %s!', 'setRawSlackQuery()'));
+      }
+
+      if (!$this->accessToken) {
+        throw new Exception(pht('You must %s!', 'setAccessToken()'));
+      }
+
+      $uri = new PhutilURI('https://slack.com/');
+      $uri->setPath('/api/'.$this->action);
+      $uri->setQueryParam('token', $this->accessToken);
+
+      $future = new HTTPSFuture($uri);
+      $future->setData($this->params);
+      $future->setMethod($this->method);
+
+      $this->future = $future;
+    }
+
+    return $this->future;
+  }
+
+  protected function didReceiveResult($result) {
+    list($status, $body, $headers) = $result;
+
+    if ($status->isError()) {
+      throw $status;
+    }
+
+    $data = null;
+    try {
+      $data = phutil_json_decode($body);
+    } catch (PhutilJSONParserException $ex) {
+      throw new PhutilProxyException(
+        pht('Expected JSON response from Slack.'),
+        $ex);
+    }
+
+    if (idx($data, 'error')) {
+      $error = $data['error'];
+      throw new Exception(pht('Received error from Slack: %s', $error));
+    }
+
+    return $data;
+  }
+
+}