S
- (Lennox and Addington County) Strathcona
- (Middlesex County) Strathroy
- (Cochrane District) Strickland
- (Parry Sound District) Strong
- (Simcoe County) Strongville
- (Hastings County) Sulphide
- (Algoma) Sulphur Island
- (Huron County) Summerhill
- (Elgin County) Summers Corners
- (Frontenac County) Sunbury
- (Durham) Sunderland
- (Simcoe County) Sunnidale
- (Simcoe County) Sunnidale Corners
- (Parry Sound District) Sunny Slope
- (Durham) Sunrise Beach
- (District Municipality of Muskoka) Sunset Beach
- (Simcoe County) Sunset Beach
- (Huron County) Sunset Beach
- (Durham) Sunset View
- (Huron County) Sunshine
- (Lambton County) Sutorville
- (York) Sutton
- (Timiskaming District) Sutton Bay
- (United Counties of Leeds and Grenville) Swan Crossing
- (Oxford County) Sweaburg
- (United Counties of Leeds and Grenville) Sweets Corners
- (District Municipality of Muskoka) Swift Rapids
- (Parry Sound District) Swindon
- (Grey County) Swinton Park
- (Lennox and Addington County) Switzerville