Kossak is a surname historically widespread in the land of Galicia, now divided between Poland and Ukraine.
Notable people with this surname include members of a famous family of Polish artists, writers and poets:
- Juliusz Kossak (1824–99), Polish painter from the partitions period, progenitor of the Kossak family
- Tadeusz Kossak (1857–1935), Polish army officer and freedom fighter
- Zofia Kossak-Szczucka (1889–1968), novelist, daughter of Tadeusz Kossak
- Wojciech Kossak (1857–1942), painter, son of Juliusz Kossak
- Jerzy Kossak (1886–1955), painter, son of Wojciech Kossak
- Gloria Kossak (1941–1991), painter and poet, daughter of Jerzy Kossak (1886–1955), sister of Simona Kossak
- Simona Kossak (1943-2007), biologist, ecologist, and professor of forest sciences, daughter of Jerzy Kossak, sister of Gloria Kossak
- Maria Pawlikowska-Jasnorzewska née Kossak (1891–1945), poet, second daughter of Wojciech Kossak
- Magdalena Samozwaniec née Kossak (1894–1972), writer, third daughter of Wojciech Kossak
- (1896–1975), painter and illustrator
Other notable bearers of the surname:
- Hryhoriy Kossak (1882-1939), commander of the Ukrainian Sich Riflemen and Ukrainian Galician Army