Siobhan-Marie O'Connor (born 29 November 1995) 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.

she has also won gold medals in 2016 at the European Championships in the same event, and in the women's 4 x 100 metres medley relay.

O'Connor announced her retirement from competitive swimming on 16 June 2021, following a long battle with ulcerative colitis.

[4] O'Connor became a swimming coach and trained Daisy Ridley for her role in the 2024 movie Young Woman and the Sea.

[6] In 2015, Siobhan was at a Team Bath warm weather training camp at Northern Arizona University at the same time four students were shot by a freshman following an altercation outside a fraternity house, leaving one dead and three wounded.