diff --git a/src/filesystem/Filesystem.php b/src/filesystem/Filesystem.php
--- a/src/filesystem/Filesystem.php
+++ b/src/filesystem/Filesystem.php
@@ -853,6 +853,48 @@
   }
 
   /**
+   * Retrieve the relative location of the specified path.
+   *
+   * This function returns the relative path from the current path to a given
+   * absolute path.
+   *
+   * @param  string  An absolute path.
+   * @return string  The relative path between the current path and the
+   *                 specified path.
+   */
+  public static function relativePath($path, $root) {
+    // Some compatibility fixes for Windows paths
+    $from = is_dir($root) ? rtrim($root, '\/').'/' : $root;
+    $to   = is_dir($path) ? rtrim($path, '\/').'/' : $path;
+    $from = str_replace('\\', '/', $from);
+    $to   = str_replace('\\', '/', $to);
+
+    $from = explode('/', $from);
+    $to   = explode('/', $to);
+
+    $rel_path = $to;
+
+    foreach ($from as $depth => $dir) {
+      // Find first non-matching directory.
+      if ($dir === $to[$depth]) {
+        // Ignore this directory.
+        array_shift($rel_path);
+      } else {
+        // Get number of remaining directories to $from.
+        $remaining = count($from) - $depth;
+        if ($remaining > 1) {
+          // Add traversals up to first matching directory.
+          $pad_length = (count($rel_path) + $remaining - 1) * -1;
+          $rel_path = array_pad($rel_path, $pad_length, '..');
+          break;
+        }
+      }
+    }
+
+    return implode('/', $rel_path);
+  }
+
+  /**
    * Test whether a path is descendant from some root path after resolving all
    * symlinks and removing artifacts. Both paths must exists for the relation
    * to obtain. A path is always a descendant of itself as long as it exists.
diff --git a/src/filesystem/__tests__/FilesystemTestCase.php b/src/filesystem/__tests__/FilesystemTestCase.php
--- a/src/filesystem/__tests__/FilesystemTestCase.php
+++ b/src/filesystem/__tests__/FilesystemTestCase.php
@@ -163,4 +163,32 @@
     }
   }
 
+  public function testRelativePath() {
+    $test_cases = array(
+      array(
+        '/foo/bar/baz',
+        '/',
+        'foo/bar/baz',
+      ),
+      array(
+        '/foo/bar/baz',
+        '/foo',
+        'bar/baz',
+      ),
+      array(
+        '/foo/foobar',
+        '/foo/bar/baz',
+        '../foobar',
+      ),
+    );
+
+    foreach ($test_cases as $test_case) {
+      list($path, $root, $expected) = $test_case;
+
+      $this->assertEqual(
+        $expected,
+        Filesystem::relativePath($path, $root));
+    }
+  }
+
 }