Petra Marčinko (born 4 December 2005) is a Croatian tennis player. Marčinko has career-high WTA rankings of 194 in singles, achieved on 7 November 2022, and 819 in doubles, set on 7 November 2022. She has won three singles and two doubles titles on the ITF Women's Circuit. Marčinko has won nine singles titles as well as seven doubles titles on the ITF Junior Circuit. She achieved her career-high junior ranking of No. 1 on 13 December 2021. At the beginning of 2022, Marčinko won her first junior Grand Slam title at the Australian Open, defeating Sofia Costoulas in straight sets.