Four Mile Bay is a bay on Trout Lake in the city of North Bay, Nipissing District in Northeastern Ontario, Canada.
The bay is about 5.4km (03.4miles) long, and is separated from the rest of Trout Lake by an equally long peninsula. It varies from 0.2to wide, the former at the mouth of the bay.
The community of Camp Champlain is on it southern shore, and Four Mile Creek enters Trout Lake at the bay.