Mokgadi Caster Semenya OIB (born 7 January 1991) is a South African middle-distance runner and 2016 Olympic gold medalist. She won gold in the women's 800 metres at the 2009 World Championships with a time of 1:55. 45, the 2016 Summer Olympics and at the 2017 World Championships in her new personal best, 1:55. 16. After the doping disqualification of Mariya Savinova, she also was awarded gold medals at the 2011 World Championships and the 2012 Summer Olympics, all in the 800 metres.