The Back River (Dogrib: Thlewechodyeth, Inuktitut: Haningayok, or Great Fish River), is a river in the Northwest Territories and Nunavut in Canada. It rises at an unnamed lake in the North Slave Region of the Northwest Territories and flows more than 974 kilometres (605 mi) mostly through Kivalliq Region, Nunavut, to its mouth at the Arctic Ocean in the Kitikmeot Region of Nunavut.