St Mary's, Ascot is a Roman Catholic independent boarding school for girls in South Ascot, Berkshire, England founded in 1885. The school now has about 360 pupils.
St Mary's, Ascot was founded by the order of nuns known as the Congregation of Jesus (CJ), formerly the Institute of the Blessed Virgin Mary (IBVM). In 1998 the school had its first lay Head Mistress, Mrs Mary Breen. Only two non-lay staff remain, Sister Michaela, a teacher, and Fr Dermot, the school's chaplain.
In 2006, the school opened its new sports centre named The Orchard Centre after the Orchard family, from which the two previous headmistresses came. The Centre was opened by the principal ballerina, Darcey Bussell. A Performing Arts Centre has also been built named 'The Rose Theatre. It opened in April 2009. Mrs Mary Breen is the current headmistress and Mrs Virginia Barker is the Deputy Head.