Derya Büyükuncu (; born July 2, 1976 in Istanbul, Turkey) is a six-time Olympic backstroke and butterfly swimmer from Turkey. The 1.90 m (6 ft 3 in) tall athlete at 90 kg (200 lb) is a member of Galatasaray Swimming. He is coached by his wife Zehra Büyükuncu.
He participated in six consecutive Summer Olympic Games: 1992 Barcelona, 1996 Atlanta, 2000 Sydney, 2004 Athens, 2008 Beijing, 2012 London. He is the first swimmer and one of the two (together with Lars Frölander) swimmers to participate in six Olympic Games.