St. Johnsville is a town in Montgomery County, New York, United States. The population was 2,631 at the 2010 census. Accounts vary as to the naming of St. Johnsville, but most of them state that the town and its village are named after an early surveyor and commissioner, Alexander St. John. Still others credit the naming of St. Johnsville to a former name for the area, St. John's Church.
The Town of St. Johnsville is in the northwest part of the county. The town contains a village, also called St. Johnsville. Both town and village are approximately halfway between Utica and Amsterdam.
The Erie Canal, as part of the Mohawk River, is at the town's south border.