Cognomen Ионг (Ионг 
, Iongh 
) , across the world, is a very rare surname. The cognomen Ионг is characteristic of Netherlands, where it is a rare surname, the United Kingdom, where it is a very rare surname, and Brazil, where it is an extremely rare surname. In absolute terms, the name is most common in Netherlands, the United Kingdom, and India. Also, Ионг is the forename as well as the last name.