Which Canadian bay forms the southern arm of Hudson Bay?

The Canadian bay forming the southern arm of Hudson Bay is James Bay.

James Bay is the broad southern extension of Hudson Bay, lying between northern Ontario and Quebec. Its waters and coastline are associated with Canada’s Arctic and sub-Arctic regions, and its largest island is Akimiski. The bay is about 443 kilometres long and reaches roughly 217 kilometres across at its widest.

James Bay is named after Thomas James, an English naval officer whose 1631 expedition explored the area. The bay’s waterways and surrounding lowlands have long supported Indigenous communities, including Cree communities along the Quebec shore and First Nations settlements in Ontario.

The region is also central to large hydroelectric developments. Rivers draining into the James Bay watershed have been dammed or diverted for major power projects, especially in northern Quebec. This makes the bay relevant not only to geography but also to Canadian energy policy and Indigenous land-rights debates.

James Bay is easy to confuse with Ungava Bay, which lies farther northeast in Quebec, or Baffin Bay, which separates parts of Canada and Greenland. Those are separate Arctic bodies of water, not the southern arm of Hudson Bay.