Lac-Long-Sud is a Unincorporated area located in Saint-Alphonse-Rodriguez; Matawinie, Quebec and has an elevation of 279 meters.

• Latitude: 46° 9' 30'' North   (decimal: 46.1583705)
• Longitude: 73° 40' 14'' West   (decimal: -73.6704186)
• Topography Feature Category: Unincorporated area
• Geographical Feature: Hameau
• Canadian Province/Territory: Quebec
• Elevation: 279 meters
• Location: Saint-Alphonse-Rodriguez; Matawinie
• Atlas of Canada Locator Map: Lac-Long-Sud
• GPS Coordinate Locator Map: Lac-Long-Sud Lat/Long