a port city in Ontario on Lake Superior
Thunder Bay may refer to several things in North America's Great Lakes region.
Thunder Bay was a federal electoral district in the northwestern part of the province of Ontario, Canada, that was represented in the Canadian House of Commons from 1968 to 1979.
Thunder Bay is a 1953 American adventure movie directed by Anthony Mann and starring James Stewart in their first non-western collaboration.
Thunder Bay is a large bay at the western end of Lake Superior.