Lac Tomassin is a Lake located in Lac-Pythonga; La Vallée-de-la-Gatineau, Quebec.

• Latitude: 46° 44' 28'' North   (decimal: 46.7411111)
• Longitude: 76° 31' 43'' West   (decimal: -76.5286111)
• Topography Feature Category: Lake
• Geographical Feature: Lac
• Canadian Province/Territory: Quebec
• Location: Lac-Pythonga; La Vallée-de-la-Gatineau
• Atlas of Canada Locator Map: Lac Tomassin
• GPS Coordinate Locator Map: Lac Tomassin Lat/Long