Lac de Gras is a lake approximately 300 kilometres (190 mi) north east of Yellowknife, in the Northwest Territories of Canada.

The lake is ultraoligotrophic but supports a slow-growing but stable population of some eight species of cold-water fishes, including round whitefish, cisco, and lake trout.

[4] Other native fish species include common whitefish, Arctic grayling, burbot, longnose sucker, and slimy sculpin.

[5] Lac du Sauvage is a small lake that drains into Lac de Gras through a 45 m (148 ft) wide and 210 m (690 ft) long stream called the Narrows.

The median flood peak discharge in the Narrows is 17.5 m3/s (620 cu ft/s) making it an important corridor for fish movements.