Blok of Cubists, Suprematists, and Constructivists aka Blok (in Polish: Blok Kubistów, Suprematystów i Konstruktywistów) was a Polish avant-garde artist collective active in the years 1924–1926 and founded by Władysław Strzemiński, Katarzyna Kobro, Henryk Berlewi, Henryk Stażewski and Mieczysław Szczuka, among others. Blok was a precursor to Praesens (1926–1930) and a.r. group (1929–1936), and all three collectives played a critical role in the development of Polish Constructivism.[1][2]