SSL
- AfreecaTV StarCraft League
- London Underground
- RoboCup Small Size League
- Rocket League
- S.S. Lazio
- S/SL programming language
- SSL (company)
- Sainsbury's
- Saitama Seibu Lions
- Samoan Sign Language
- Secure Sockets Layer
- Selangor Sign Language
- Self-supervised learning
- Semi-supervised learning
- Serbian SuperLiga
- Sesame Street Live
- Shakey's Super League
- Single stuck line
- Sisters of St. Louis
- Social Science Library, Oxford
- Sodium stearoyl lactylate
- Solid State Logic
- Solid-state lighting
- Somali Sign Language
- South Salt Lake, Utah
- South Shore League
- South Shore Line
- Soviet Second League
- Soviet Second League B
- Space Sciences Laboratory
- Space Systems Laboratory
- Space Systems Laboratory (MIT)
- Space Systems Laboratory (Maryland)
- Spanish Sign Language
- Spanish as a Second Language
- Standard sea level
- Star Sailors League
- StarCraft II StarLeague
- Start-stop logic
- Sumatra squall lines
- Super Mario 64
- Super Smash Bros.
- Super Smash Land
- Swedish Sign Language
- Swedish Super League (men's floorball)
- Swedish Super League (women's floorball)
- Swiss Super League
- System Simulation Ltd
- Transport Layer Security