- Sheldrake Island
- Sheldrake Ledge
- Shingle Island
- Ship Island
- Sister Islands
- Sloop Island
- Smuttynose Island
- Snake Island
- South Blue Hill
- South Brooksville
- South Deer Isle
- South Gouldsboro
- South Hancock
- South Orland
- South Penobscot
- South Surry
- Southern Mark Island
- Soward Island
- Sparks Island
- Spectacle Island
- Spectacle Island
- Sprout Island
- Spruce Island
- Squid Island
- Stave Island
- Stave Island
- Steep Landing
- Steres Island
- Steve Island
- Stinson Neck