SLO may refer to:
- Salem–Leckrone Airport (IATA airport code), near Salem, Illinois, US
- San Luis Obispo, California, US
- Scanning laser ophthalmoscopy, an eye examination method
- Service-level objective, part of a customer agreement
- SLO (EP), by Jess Mills
- Streptolysin O, an exotoxin produced by streptococci
- Student Learning Objectives, an assessment tool used by teachers
- Supporter liaison officer, a person within an association sports club
- Slovenia (international vehicle registration code and IOC country code)