wp_create_category()

wp_create_category( string $category_name, int $category_parent ): int

function wp_create_category( $category_name, $category_parent = 0 ) {
	$id = category_exists( $category_name, $category_parent );
	if ( $id ) {
		return (int) $id;
	}

	return wp_insert_category(
		array(
			'cat_name'        => $category_name,
			'category_parent' => $category_parent,
		)
	);
}