Siobhan-Marie O'Connor is a former English competitive swimmer who has represented Great Britain at the Olympic Games, the FINA World Aquatics Championships and the LEN European Aquatics Championships, and England at the Commonwealth Games. A specialist in the 200 metres individual medley, she is the 2014 Commonwealth Games champion in the event, and has won silver medals in the same event at the 2016 Summer Olympics, the 2015 World Aquatics Championships, 2016 European Aquatics Championships, the 2014 World Short-Course Championships and the 2013 and 2015 European Short Course Championships – on each occasion behind World and Olympic champion Katinka Hosszú. With six Commonwealth Games medals in total from 2014, O'Connor was England's most decorated athlete at those Games.