Northwestern Ontario is a portion of Ontario, Canada. The most prominent city in Northwestern Ontario is Thunder Bay (formerly the cities of Fort William and Port Arthur), but other towns include Marathon, Wawa, Schreiber, Nipigon, Sioux Lookout, Dryden, Atikokan, Fort Frances, and Kenora among others.
This region is administered in hockey matters by the Thunder Bay Amateur Hockey Association.
From 1919 until the 1970's, the regional champions usually advanced to the Western Canada Allan Cup and Memorial Cup playoffs. Occasionally the team would play in the Eastern Canada playoffs. Some seasons the senior teams would join with the Manitoba squads in one league.