Nettilling Lake, 5542 km2, elevation 30 m, max length 123 km, is located toward the south end of Baffin Island in the Great Plain of the Koukdjuak, about 110 km southwest of Auyuittuq National Park and 280 km northwest of Iqaluit. The name is of Inuktitut origin but its meaning is unclear.
The largest lake in Nunavut and the eleventh largest in Canada, Nettilling is fed by Amadjuak Lake and several other small lakes and streams. Composed of three bays (Mirage, Camsell and Burwash), its eastern half is dotted with numerous islands; the western half is deeper with no islands. The lake empties into Foxe Basin from its west shore via the very shallow Koukdjuak River. Ice-covered for most of the year, only 3 species of fish have been recorded to inhabit its waters: Arctic char and 2 species of stickleback. The area around the lake and south to Amadjuak Lake is important for caribou.