Marta Olehivna Kostyuk (Ukrainian: Марта Олегівна Костюк; born 28 June 2002) is a Ukrainian tennis player.
Marta is the daughter of Oleh Kostyuk and his wife, Talina (née Beyko). Her father was the technical director of the Kiev junior tennis tournament "Antey Cup", and her mother was a professional tennis player representing Ukraine in the 1990s who reached a career-high WTA ranking of No. 391, winning a $10,000 title in her home city of Kiev in October 1994. With both her parents having a tennis background, Marta started playing tennis in her young childhood at the Antey Tennis Club on the west side of Kiev. Marta described her initial experience in tennis at age 5: "My mom was always working a lot as a coach, and the first time I went to the courts to train, I just understood that if I started doing tennis, I'd get to spend more time with my mom. So that was kind of my motivation – if I played tennis, I'd be around her more often". One of her first coaches was her native uncle Taras Beyko, a respected player for the USSR and Ukraine in the late 1980s and early 1990s.