St. Mary's was the site of a planned village within early Victoria County, in the Canadian province of Ontario.
The site was laid aside in the surveying of the county in the 1830s, but was later found to be unusable when limestone was discovered two inches below the ground.
The property of the reserved town site remained in the hands of the government for some time, until eventually being absorbed into the adjoining Laidlaw estate.
The former St. Mary's site was chosen as the starting point for the canal, which was dug westward through the rock to a swamp along the Grass River.
The service was discontinued in 1872, when the Toronto and Nipissing Railway established a station in Victoria Road and a post office was built there.