Nettilling Lake (/ˈnɛtʃ.ɪl.ɪŋ/) is a cold freshwater lake located toward the south end of Baffin Island in the Qikiqtaaluk Region, Nunavut, Canada. It is the 30th largest lake in the world by area, and the world's largest lake on an island, with an area of 5,542 km (2,140 sq mi) and a maximum length of 123 km (76 mi). The lake is in the Great Plain of the Koukdjuak about 280 km (170 mi) northwest of Iqaluit. The Arctic Circle crosses the lake. The lake's name is of Inuktitut origin, coming from the word for the adult ringed seal (netsilak). Franz Boas explored its southern shore in 1884.

Nettilling is the largest lake in Nunavut. It is fed by the second largest lake on Baffin Island, Amadjuak Lake; as well as several other smaller lakes and streams. It empties west via the very shallow Koukdjuak River into Foxe Basin. The eastern half has many small islands and the western half is deeper with no islands. The lake is frozen for most of the year. Ringed seals live in the lake, along with three recorded species of fish: the Arctic char, the ninespine, and three-spined stickleback. The tundra around the lake and south to Amadjuak Lake is important for barren-ground caribou feeding and calving.

Nettilling Lake is the eleventh largest in Canada, being one of the largest lakes entirely within Canada.

• List of lakes of Nunavut
• List of lakes of Canada

• Evans, David (30 September 2021). "Nettilling Lake". The Canadian Encyclopedia. Historica Canada.
• "Nettilling Lake and Amadjuak Lake". Canada's Polar Environments. Archived from the original on 11 February 2021.

• "Baffin Island map and info". Canada's Polar Environments. Archived from the original on 26 June 2021.