Surname Яцек (Jacek 
, Яцек 
) , in the entire world, is a widespread family name. The surname Яцек is characteristic of Eastern Europe, particularly Poland, where it is a prevalent surname, Hungary, where it is quite a rare surname, and Slovakia. Measured by absolute frequency, it is the most numerous in Poland, the United States, and Germany. Much less frequently, Яцек is the forename as well as the last name.