S
- (United Counties of Leeds and Grenville) Selton
- (Peterborough County) Selwyn
- (Comtés unis de Prescott et Russell) Senecal
- (Frontenac County) Seouls Corners
- (Parry Sound District) Seven Mile Narrows
- (Simcoe County) Severn Bridge
- (Simcoe County) Severn Falls
- (Elgin County) Seville
- (Renfrew County) Shady Nook
- (Cochrane District) Shallow Lake
- (Wellington County) Shands
- (United Counties of Leeds and Grenville) Shanes
- (Hastings County) Shanick
- (District Municipality of Muskoka) Shannon Hall
- (Frontenac County) Sharbot Lake
- (Middlesex County) Sharon
- (Parry Sound District) Shawanaga Landing
- (Ottawa) Sheahan Estates
- (United Counties of Leeds and Grenville) Sheatown
- (Parry Sound District) Shebeshekong
- (Elgin County) Shedden
- (Ottawa) Sheffield Glen
- (United Counties of Leeds and Grenville) Sheldon's Corners
- (Rainy River District) Shenston
- (Huron County) Sheppardton
- (Regional Municipality of Waterloo) Shep's Subdivision
- (Algoma) Sherwood
- (United Counties of Leeds and Grenville) Sherwood Springs
- (Lambton County) Shetland
- (Renfrew County) Shields Crossing