diff --git a/src/applications/files/config/PhabricatorFilesConfigOptions.php b/src/applications/files/config/PhabricatorFilesConfigOptions.php
--- a/src/applications/files/config/PhabricatorFilesConfigOptions.php
+++ b/src/applications/files/config/PhabricatorFilesConfigOptions.php
@@ -212,6 +212,16 @@
             'must be installed and the "%s" binary must be available to '.
             'the webserver for this to work.',
             'convert')),
+     $this->newOption('files.maximum-file-size', 'int', 0)
+       ->setDescription(
+         pht(
+           'You can set a limit for the maximum byte size for files uploaded. '.
+           'Attempting to upload a file larger than the specified size will '.
+           'cause the upload to fail. Values smaller than or equal to zero '.
+           'will be ignored. Specify a value in bytes.'))
+       ->setSummary(pht('Global cap for files uploaded (bytes).'))
+       ->addExample(1048576, pht('Limit files to 1 MB'))
+       ->addExample(10485760, pht('Limit files to 10 MB')),
 
     );
   }
diff --git a/src/applications/files/storage/PhabricatorFile.php b/src/applications/files/storage/PhabricatorFile.php
--- a/src/applications/files/storage/PhabricatorFile.php
+++ b/src/applications/files/storage/PhabricatorFile.php
@@ -327,12 +327,28 @@
     return $file;
   }
 
+  private static function assertNotExceedingSizeLimit($size) {
+
+    $max_file_size = PhabricatorEnv::getEnvConfig('files.maximum-file-size');
+    $exceeds_limit = $max_file_size > 0 && $size > $max_file_size;
+
+    if ($exceeds_limit) {
+      throw new Exception(
+        pht(
+          'The file uploaded is bigger than the configured maximum file size'.
+          ' (%s).',
+          phutil_format_bytes($max_file_size)));
+    }
+  }
+
   private static function buildFromFileData($data, array $params = array()) {
 
+    $size = strlen($data);
+    self::assertNotExceedingSizeLimit($size);
+
     if (isset($params['storageEngines'])) {
       $engines = $params['storageEngines'];
     } else {
-      $size = strlen($data);
       $engines = PhabricatorFileStorageEngine::loadStorageEngines($size);
 
       if (!$engines) {
diff --git a/src/applications/files/storage/__tests__/PhabricatorFileTestCase.php b/src/applications/files/storage/__tests__/PhabricatorFileTestCase.php
--- a/src/applications/files/storage/__tests__/PhabricatorFileTestCase.php
+++ b/src/applications/files/storage/__tests__/PhabricatorFileTestCase.php
@@ -603,4 +603,50 @@
       pht('newChunkedFile returns a PhabricatorFile'));
   }
 
+  public function newRandomFile(int $size) {
+    $engine = new PhabricatorTestStorageEngine();
+
+    $data = Filesystem::readRandomCharacters($size);
+    $params = array(
+      'name' => 'test.dat',
+      'storageEngines' => array(
+        $engine,
+      ),
+    );
+
+    PhabricatorFile::newFromFileData($data, $params);
+  }
+
+  public function testMaximumFileSize() {
+    $env = PhabricatorEnv::beginScopedEnv();
+
+    $env->overrideEnvConfig('files.maximum-file-size', -1024);
+    $this->tryTestCases(
+      array(
+        '512 KB' => 512,
+        '1 MB' => 1024,
+        '2 MB' => 2048,
+      ),
+      array(
+        true,
+        true,
+        true,
+      ),
+      array($this, 'newRandomFile'));
+
+    $env->overrideEnvConfig('files.maximum-file-size', 1024);
+    $this->tryTestCases(
+      array(
+        '512 KB' => 512,
+        '1 MB' => 1024,
+        '2 MB' => 2048,
+      ),
+      array(
+        true,
+        true,
+        false,
+      ),
+      array($this, 'newRandomFile'));
+  }
+
 }