DSI is an initialism for the following companies:
- Daiichi Sankyo, Incorporated
- Data Sciences International, a company in Saint Paul, United States
- Dave Smith Instruments, an American synthesizer company
- Deep Space Industries, American-based asteroid mining startup
- Deep Springs International
- Delphi Schools, Inc.
- Delphine Software International, a now bankrupt software company
- Destination Software, Inc., a video game company
- Distinctive Software Inc., a video game company
- Diversified Specialty Institute Holdings, Inc., a US-based healthcare group
- Drivetrain Systems International, an Australian automotive transmissions manufacturer
- DYWIDAG Systems International, an international supplier of ground anchors and post-tensioning systems
- State Hydraulic Works (Turkey) (Turkish: Devlet Su İşleri (DSİ)), a state agency in Turkey
- Decision Sciences Institute, a professional association focusing on the application of quantitative research and qualitative research to the decision problems of individuals, organizations, and society.
- Deutsche Schule Istanbul, a private high school in Istanbul