St. Mary's Island is a Island located in Algoma, Ontario.

• Latitude: 46° 30' 44'' North   (decimal: 46.5122222)
• Longitude: 84° 21' 17'' West   (decimal: -84.3547222)
• Topography Feature Category: Island
• Geographical Feature: Island
• Canadian Province/Territory: Ontario
• Location: Algoma
• Atlas of Canada Locator Map: St. Mary's Island
• GPS Coordinate Locator Map: St. Mary's Island Lat/Long