Northwestern Ontario

Northwestern Ontario
Secondary region
Country	Canada
Province	Ontario
Largest city	Thunder Bay 108,843 (2021)
Area
• Total	526,417.35 km2 (203,250.88 sq mi)
Population  (2021)
• Total	232,299
• Density	0.5/km2 (1/sq mi)
Time zones	UTC−6 (CST)
• Summer (DST)	UTC−5 (CDT)
	UTC−5 (EST)
• Summer (DST)	UTC−4 (EDT)

Northwestern Ontario is a secondary region of Northern Ontario in the Canadian province of Ontario which lies north and west of Lake Superior and west of Hudson Bay and James Bay. It includes most of subarctic Ontario. Its western boundary is the Canadian province of Manitoba, which disputed Ontario's claim to the western part of the region. Ontario's right to Northwestern Ontario was determined by the Judicial Committee of the Privy Council in 1884^[1] and confirmed by the Canada (Ontario Boundary) Act, 1889, of the Parliament of the United Kingdom. In 1912, the Parliament of Canada by the Ontario Boundaries Extension Act gave jurisdiction over the District of Patricia to Ontario, thereby extending the northern boundary of the province to Hudson Bay.

For some purposes, Northwestern Ontario and Northeastern Ontario are treated as separate regions, while for other purposes they are grouped together as Northern Ontario.