Family name Ioannu (Ioannu 
, Иоанну 
) , in the world, is a rare surname. The cognomen Ioannu is habitual in Bulgaria, where it is a rare surname, Greece, where it is a very rare surname, and Argentina. In absolute terms, it is the most numerous in Bulgaria, Russia, and Argentina. Very seldom, Ioannu is the forename as well as the last name.