ASW, a three-letter abbreviation, may refer to:
- Air Southwest, a British airline
- Ambrosia Software, a predominantly Macintosh software company.
- Anti-submarine warfare
- Artificial seawater
- Aswan International Airport
- All Star Wrestling, a professional wrestling promotion based in Liverpool, England
- aSmallWorld, an online social network service
- A Softer World, a webcomic
- Arc System Works, a video game developer
- Actual silver weight, a numismatic term
- American School of Warsaw, an international school in Warsaw, Poland.
- African ancestry in the southwestern United States, one of the populations of the International HapMap Project.