Cognomen Blagii (Blagii 
, Благий 
) , throughout the world, is a rare last name. The cognomen Blagii is habitual in Eastern Europe, particularly Ukraine, where it is quite a rare surname, Russia, where it is a rare surname, and Belarus, where it is a very rare surname. Not in comparison with a country's population, this name is the most popular in Ukraine, Russia, and Kazakhstan.