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- (Renfrew County) Jewellville
- (United Counties of Leeds and Grenville) Johnstown
- (Peterborough County) Juniper Island
- (United Counties of Leeds and Grenville) Junetown
- (United Counties of Leeds and Grenville) Judgeville
- (Timiskaming District) Judge
- (District Municipality of Muskoka) Juddhaven
- (Regional Municipality of Waterloo) Josephsburg
- (United Counties of Leeds and Grenville) Jones Falls
- (Ottawa) Johnston Corners
- (Lanark County) Joes Lake
- (Ottawa) Jockvale
- (Simcoe County) Jack Lake
- (Comtés unis de Prescott et Russell) Jessups Falls
- (Dufferin County) Jessopville
- (Peterborough County) Jermyn
- (United Counties of Leeds and Grenville) Jellyby
- (Thunder Bay District) Jelly
- (Simcoe County) Jarratt
- (Huron County) Jamestown
- (Elgin County) Jaffa
- (Grey County) Jackson
- (Peterborough County) Jack Lake
- (Haldimand County) Jarvis