Mokgadi Caster Semenya OIB (born 7 January 1991) is a South African middle-distance runner and winner of two Olympic gold medals and three World Championships in the women's 800 metres. She first won gold at the World Championships in 2009, and went on to win at the 2016 Olympics, and 2017 World Championships, where she also won a bronze medal in the 1500 metres. After the doping disqualification of Mariya Savinova, she was also awarded gold medals for the 2011 World Championships and the 2012 Olympics.