diff --git a/src/wp-includes/category-template.php b/src/wp-includes/category-template.php
index fbf9b9326e..232f147f96 100644
--- a/src/wp-includes/category-template.php
+++ b/src/wp-includes/category-template.php
@@ -314,6 +314,7 @@ function category_description( $category = 0 ) {
  *
  * @since 2.1.0
  * @since 4.2.0 Introduced the `value_field` argument.
+ * @since 4.6.0 Introduced the `required` argument.
  *
  * @param string|array $args {
  *     Optional. Array or string of arguments to generate a categories drop-down element.
@@ -351,6 +352,8 @@ function category_description( $category = 0 ) {
  *     @type string|array $taxonomy          Name of the category or categories to retrieve. Default 'category'.
  *     @type bool         $hide_if_empty     True to skip generating markup if no categories are found.
  *                                           Default false (create select element even if no categories are found).
+ *     @type bool         $required          Whether the <select> element should have the HTML5 'required' attribute.
+ *                                           Default false.
  * }
  * @return string HTML content only if 'echo' argument is 0.
  */
@@ -376,6 +379,7 @@ function wp_dropdown_categories( $args = '' ) {
 		'hide_if_empty'     => false,
 		'option_none_value' => -1,
 		'value_field'       => 'term_id',
+		'required'          => false,
 	);
 
 	$defaults['selected'] = ( is_category() ) ? get_query_var( 'cat' ) : 0;
@@ -414,9 +418,10 @@ function wp_dropdown_categories( $args = '' ) {
 	$name = esc_attr( $r['name'] );
 	$class = esc_attr( $r['class'] );
 	$id = $r['id'] ? esc_attr( $r['id'] ) : $name;
+	$required = $r['required'] ? 'required' : '';
 
 	if ( ! $r['hide_if_empty'] || ! empty( $categories ) ) {
-		$output = "<select name='$name' id='$id' class='$class' $tab_index_attribute>\n";
+		$output = "<select $required name='$name' id='$id' class='$class' $tab_index_attribute>\n";
 	} else {
 		$output = '';
 	}
diff --git a/tests/phpunit/tests/category/wpDropdownCategories.php b/tests/phpunit/tests/category/wpDropdownCategories.php
index 4750370222..38d563b05f 100644
--- a/tests/phpunit/tests/category/wpDropdownCategories.php
+++ b/tests/phpunit/tests/category/wpDropdownCategories.php
@@ -153,4 +153,72 @@ class Tests_Category_WpDropdownCategories extends WP_UnitTestCase {
 			$this->assertNotContains( 'value="' . $_cat->slug . '" selected="selected"', $found );
 		}
 	}
+
+	/**
+	 * @ticket 31909
+	 */
+	public function test_required_true_should_add_required_attribute() {
+		// Create a test category.
+		$cat_id = self::factory()->category->create( array(
+			'name' => 'Test Category',
+			'slug' => 'test_category',
+		) );
+
+		$args = array(
+			'show_option_none'  => __( 'Select one', 'text-domain' ),
+			'option_none_value' => "",
+			'required'          => true,
+			'hide_empty'        => 0,
+			'echo'              => 0,
+		);
+		$dropdown_categories = wp_dropdown_categories( $args );
+
+		// Test to see if it contains the "required" attribute.
+		$this->assertRegExp( '/<select[^>]+required/', $dropdown_categories );
+	}
+
+	/**
+	 * @ticket 31909
+	 */
+	public function test_required_false_should_omit_required_attribute() {
+		// Create a test category.
+		$cat_id = self::factory()->category->create( array(
+			'name' => 'Test Category',
+			'slug' => 'test_category',
+		) );
+
+		$args = array(
+			'show_option_none'  => __( 'Select one', 'text-domain' ),
+			'option_none_value' => "",
+			'required'          => false,
+			'hide_empty'        => 0,
+			'echo'              => 0,
+		);
+		$dropdown_categories = wp_dropdown_categories( $args );
+
+		// Test to see if it contains the "required" attribute.
+		$this->assertNotRegExp( '/<select[^>]+required/', $dropdown_categories );
+	}
+
+	/**
+	 * @ticket 31909
+	 */
+	public function test_required_should_default_to_false() {
+		// Create a test category.
+		$cat_id = self::factory()->category->create( array(
+			'name' => 'Test Category',
+			'slug' => 'test_category',
+		) );
+
+		$args = array(
+			'show_option_none'  => __( 'Select one', 'text-domain' ),
+			'option_none_value' => "",
+			'hide_empty'        => 0,
+			'echo'              => 0,
+		);
+		$dropdown_categories = wp_dropdown_categories( $args );
+
+		// Test to see if it contains the "required" attribute.
+		$this->assertNotRegExp( '/<select[^>]+required/', $dropdown_categories );
+	}
 }