LSI
- Hard water
- LSI (Love Sex Intelligence)
- LSI Corporation
- LTI system theory
- La Salle Institute
- Labour and Socialist International
- Lake Superior and Ishpeming Railroad
- Landing ship, infantry
- Large-scale integration
- Latent semantic indexing
- Lear Siegler Incorporated
- Lingkaran Survei Indonesia
- Linguistic Survey of India
- Long-string instrument
- Lynch Syndrome International
- PDP-11
- Socialist Movement for Integration
- Socionics
- Sumburgh Airport