Maria Koszutska (pseudonym Wera Kostrzewa) (2 February 1876, Główczyn - 9 July 1939, Moscow) was a leader and theoretician of the Polish Socialist Party "Left" faction (Polska Partia Socialistyczna, PPS  — Lewica) and later of the Communist Party of Poland (KPP). She joined the PPS in 1902 and was a member of the executive of the splinter PPS-Left, and the KPP from 1918. With interruptions, she sat on the Central Committee of the KPP 1918–29 and its politburo 1923-29.

After 1929 she lived in the USSR, working in a publishing house. She opposed the Stalinization of the KPP and the Communist International. Arrested in 1937 during Stalinist purges, she died in prison in 1939.