river in northeastern Manitoba, Canada, rising from several lakes in the central part of the province and flowing northeastward for 300 miles (500 km) across the Canadian Shield (a region of rocky, ice-smoothed hills dotted with lakes) to enter Hudson Bay at York Factory. The river, named for Sir James Hayes of the Hudson's Bay Company, was, together with the Nelson River, an important route from the company's port of York Factory to Lake Winnipeg and the interior.