O.S.T.R. (also known as Ostry, real name Adam Ostrowski, born May 15, 1980 in Łódź, Poland) is a recognized Polish hip-hop artist. As a rapper and producer, O.S.T.R. has managed to stay true to the rap game despite his big success in Poland. He has also stayed loyal to the underground audience as opposed to more commercial rappers supported by the mass-media.