Sebastien Daniel Rousseau (born 10 September 1990) is a competition swimmer who has represented South Africa in three Summer Olympics and other international swimming championships.

Rousseau is the South African record holder in the 400m Individual Medley (LCM) with a time of 4:11.11, which he achieved while winning the event at the 2013 U.S.

[3] At the 2016 Summer Olympics, he competed in the 400 m individual medley where he finished 21st in the heats with a time of 4:18.72 and did not qualify for the final.

[5] He was part of South Africa's 4 × 200 m freestyle relay team that finished 10th in the heats and did not qualify for the final.

[6] Rousseau retired from competitive swimming following the Rio Olympic Games in 2016.