Liber, properly Marcin Piotrowski (b. July 10, 1981 in Oborniki) – Polish rapper and songwriter. A former member of the hip-hop group Ascetoholix, in which he performed together with his cousin Christopher “Kris” Piotrowski and Dominic “Donia” Grabowski. Also co-founded the short-lived project with Rio Boss with Cuba Mańkowski and Sylwia Grzeszczak. Since 2004 he has run a solo artistic activity. Liber also worked, among others, with such performers as Agnieszka Wlodarczyk, Mezo, Slums Attack and Goshia Andrzejewicz.