Hudson Bay (Southern East Cree: ᐐᓂᐯᒄ, romanized: Wînipekw; Northern East Cree: ᐐᓂᐹᒄ, romanized: Wînipâkw; Inuktitut: ᑲᖏᖅᓱᐊᓗᒃ ᐃᓗᐊ, romanized: Kangiqsualuk ilua or Inuktitut: ᑕᓯᐅᔭᕐᔪᐊᖅ, romanized: Tasiujarjuaq; French: baie d'Hudson), sometimes called Hudson's Bay (usually historically), is a large body of saltwater in northeastern Canada with a surface area of 1,230,000 km² (470,000 sq mi). It is located north of Ontario, west of Quebec, northeast of Manitoba and southeast of Nunavut, but politically entirely part of Nunavut. It is an inland marginal sea of the Arctic Ocean. It drains a very large area, about 3,861,400 km² (1,490,900 sq mi), that includes parts of southeastern Nunavut, Alberta, Saskatchewan, Ontario, Quebec, all of Manitoba, and parts of the U.S. states of North Dakota, South Dakota, Minnesota, and Montana. Hudson Bay's southern arm is called James Bay.

The Eastern Cree name for Hudson and James Bay is Wînipekw (Southern dialect) or Wînipâkw (Northern dialect), meaning muddy or brackish water. Lake Winnipeg is similarly named by the local Cree, as is the location for the city of Winnipeg.