Cognomen Петръ (Petr 
, Петръ ) , across the world, is a common last name. The cognomen Петръ is characteristic of Czechia, where it is a common surname, Reunion, where it is quite a common surname, and Slovakia, where it is quite a rare surname. Measured by absolute frequency, it is commonest in Czechia, the United States, and China. More frequently, Петръ is the forename as well as the last name.