Hudson Bay, a body of water in northeastern Canada. It is one of the largest ocean inlets in the world, with an area of about 317,500 square miles (822,300 km)—roughly three times the size of the Great Lakes combined. Hudson Bay is linked to the Atlantic Ocean by Hudson Strait. James Bay is the southernmost extension. Maximum dimensions are about 850 miles (1,370 km) north-south and about 650 miles (1,050 km) east-west; maximum depth is about 850 feet (260 m).

The bleak, desolate shores of Hudson Bay are almost unpopulated. The eastern shore is rocky and dotted with islands; much of the western shore is low and swampy. A number of rivers empty into the bay, including the Churchill, Nelson, Severn, and Albany. The main occupations of the region are trapping and fishing.

Hudson Bay is open to shipping from mid-July through most of October. Churchill, Manitoba, on the western shore, is its chief port and has rail connections with southern Canada.

Henry Hudson discovered Hudson Bay in 1610. In 1670 the English Crown gave the Hudson's Bay Company a charter granting it exclusive trading rights to the bay's entire drainage basin. The French ceded their bay forts to Britain in 1713. Canada took over control of the bay area from the Hudson's Bay Company in 1869.