The Beaufort Sea (French: mer de Beaufort) is a marginal sea of the Arctic Ocean, located north of the Northwest Territories, the Yukon, and Alaska, west of Canada's Arctic islands. The sea is named after hydrographer Sir Francis Beaufort. The major Mackenzie River empties into the Canadian part of the sea, west of Tuktoyaktuk, which is one of the few permanent settlements on the sea shores.

The sea, characterized by severe climate, is frozen over most of the year; only a narrow pass up to 100 km (62 mi) opens in August–September near its shores. The seacoast was populated about 30,000 years ago, but the population density is very low. The sea contains significant resources of petroleum and natural gas under its shelf, such as the Amauligak field. They were discovered in the period between 1950s and 1980s, and their exploration became the major human activity in the area since the 1980s. The traditional occupations of fishery and whale and seal hunting are practiced only locally, and have no commercial significance. As a result, the sea hosts one of the largest colonies of beluga whales, and there is no sign of overfishing. There is a long-standing dispute between the United States and Canada over the sea border area, but significant steps have been taken in 2010 toward its resolution.