St Mary's School was an independent Roman Catholic day and boarding school for girls, founded in 1945 in a rural setting near Shaftesbury, England. The school had a sixth form and was a member of the Girls' Schools Association. After operating at a loss for some time, the school closed in July 2020. Although the school's postal address was in Dorset, its site lay just over the county border in Wiltshire, within the parish of Donhead St Mary.