Sarah Lucy Hardcastle (born 9 April 1969), also known by her married name Sarah Thomas,[1] is a British former competitive swimmer who represented Great Britain in the Olympics, world championships and European championships, and swam for England in the Commonwealth Games.

She retired from the sport in 1986 but returned in 1993, winning gold at the World Short Course Championships for the 800-metre freestyle in 1995 and reaching the final of the same event at the 1996 Summer Olympics.

[5] Hardcastle initially retired from competitive swimming in 1986 at the age of 17; in a 2012 interview she said that after years of training she had wanted to have a normal teenage life.

[7] She participated in Prince Edward's charity television special The Grand Knockout Tournament in 1987.

[7] Her mother, Ann Hardcastle, is a former swimming coach who taught several British elite swimmers including Mark Foster.