RSL
- RAISE Specification Language
- RLS (disambiguation)
- Radcliffe Science Library
- Real Salt Lake
- Really Simple Licensing
- Received Signal Level
- Registered Social Landlord
- Relative sea level
- RenderMan Shading Language
- Rennellese Sign Language
- Reserve static line
- Restricted Service Licence
- Returned and Services League of Australia
- Revolutionary Socialist League (disambiguation)
- Robert Sean Leonard
- Roshn Saudi League
- Royal Society of Literature
- Royal Standard de Liège
- Rugby Super League (United States)
- Russian Sign Language
- Russian State Library
- Russian Superleague
- Seasonal flows on warm Martian slopes