The Beaufort Sea (mer de Beaufort) is the portion of the Arctic Ocean located north of the Northwest Territories, the Yukon, and Alaska and west of Canada's Arctic islands. Its northwestern boundary is defined by a line connecting Point Barrow, Alaska, and Lands End, Prince Patrick Island. It is about 450,000 km² (170,000 mi²) in area. The sea is named after Irish hydrographer Sir Francis Beaufort.
The large Mackenzie River empties into the sea as do other smaller rivers. It is an important habitat for whales and sea birds and is still relatively untouched by commercial traffic.
The Beaufort Sea is also the location of what are believed to be significant petroleum reserves beneath the seabed, a continuation of proven reserves in the nearby Mackenzie River and North Slope. The Beaufort Sea was first explored in the 1960s and the Amauligak Project of 1986 began operating the first functioning oil platform.
There is an ongoing dispute between Canada and the United States over the delimitation of part of the maritime section of the International Boundary in the Beaufort Sea. Canada claims the maritime boundary to be along the 141st meridian out to a distance of 200 nautical miles (370 km), following the Alaska-Yukon land border. The United States claims the boundary line to be perpendicular to the coast out to a distance of 200 nautical miles (370 km), following a line of equidistance from the coast. This difference creates a wedge that is claimed by both nations. This dispute has taken on increased significance due to the possible presence of petroleum reserves within the wedge. Both nations have put petroleum exploration rights up for bid on sections within this disputed wedge.
The entire Beaufort Sea is totally frozen during much of the year. The permanent ice-pack covers the northern edge of the Beaufort Sea year-round.