Lake Hazen is often called the northernmost lake of Canada, in the northern part of Ellesmere Island, Nunavut, but detailed maps show several smaller lakes up to more than 100km farther north on Canada's northernmost island. Turnabout Lake is immediately northeast of the northern end of Hazen lake. Still further north are the Upper and Lower Lakes, with Upper Dumbell Lake 5.2km southwest of Alert, Canada's northernmost settlement on the coast of Lincoln Sea, Arctic Ocean.
The northeastern end of Lake Hazen is 118km southwest of Alert. Lake Hazen is the world's largest lake north of the Arctic Circle by volume. By surface area, it is third largest, after Lake Taymyr in Russia and Lake Inari in Finland. Lake Hazen is 74km long and up to 12km wide, with an area of 537.5km2. It stretches in a southwest-northeast direction from to . The lake is up to 269m deep and has an estimated volume of 51.4 km². The shoreline is 185km long and 158m above sea level. It has several islands, the largest of them being Johns Island, which is 7km long and less than 1km wide, also extending in a southwest-northeast direction like the lake itself. Other islands include Gatter Island, Clay Island Whisler Island, and Dyas Island (both close to the southern shore). The lake is covered by ice about ten months a year. It is fed by glaciers from the surrounding Eureka Uplands (Palaeozoic rocks north of the lake, rising up to 2500m above sea level), most importantly Henrietta Nesmith and the Gilmour Glaciers, and drained by 15km long Ruggles River which flows into Chandler Fjord on the northern east coast of Ellesmere Land. The lake is flanked by the Arctic Cordillera.
The area around the lake is a thermal oasis within a polar desert, with summer temperatures up to 20C.
The lake is part of Quttinirpaaq National Park.
Artifacts of Thule civilization were discovered near Lake Hazen in 2004. Thule preceded the Inuit. In 1882, Augustus Greely discovered the lake during his expedition 1881-1883. Greely's base camp for the exploration was Fort Conger at the northeastern shore of Ellesmere Island, at, which was established as part of the first International Polar Year. Greely named the lake in honor of general William Babcock Hazen, who had organized the expedition. Camp Hazen was established on the northern shore of the lake in 1957 during the International Geophysical Year (IGY), and has been used by various scientific parties since then.
Lake Hazen is populated by a larger and a smaller morphotype of Arctic char. Recent studies indicate they are not anadromous, though Inuit traditional knowledge states otherwise.