St. Marys is a town in southwestern Ontario, Canada. It is located on the Thames River southwest of Stratford in Perth County, and surrounded by the Township of Perth South. The town is also known by its nickname, "The Stone Town", due to the abundance of limestone in the surrounding area, giving rise to a large number of limestone buildings and homes throughout the town.
St. Marys Cement, a large cement producer founded in the town, capitalized on this close feedstock, and grew to be a major producer of cement in the province of Ontario. It is the burial place of Arthur Meighen, Canada's 9th Prime Minister. Timothy Eaton, who went on to become one of Canada's greatest retailers, opened his first businesses in Canada in St. Marys and nearby Kirkton, Ontario. St. Marys is home to the Canadian Baseball Hall of Fame.