Lac Castor is a Lake located in Rivière-Éternité; Le Fjord-du-Saguenay, Quebec.

• Latitude: 48° 17' 0'' North   (decimal: 48.2833619)
• Longitude: 70° 23' 23'' West   (decimal: -70.3897903)
• Topography Feature Category: Lake
• Geographical Feature: Lac
• Canadian Province/Territory: Quebec
• Location: Rivière-Éternité; Le Fjord-du-Saguenay
• Atlas of Canada Locator Map: Lac Castor
• GPS Coordinate Locator Map: Lac Castor Lat/Long