St. Marys is a city and the county seat of Pleasants County, West Virginia, United States. The population was 1,847 at the 2020 census. It is part of the Parkersburg–Vienna metropolitan area. St. Marys was established in 1849 by Alexander Creel, who is said to have had a vision of Mary while passing the townsite by boat on the Ohio River.

Pleasants County is a county located in the U.S. state of West Virginia. At the 2020 census, the population was 7,653. Its county seat is St. Marys.