OST
- Chris Douglas (musician)
- Fred Emery
- Lustre (file system)
- O.S.T. (album)
- OST Family
- Office of Science and Technology
- Office of Secure Transportation
- Offline Storage Table
- Old Spanish Trail (auto trail)
- Oligosaccharyltransferase
- Open-space technology
- Orbit stabiliser theorem
- Order of the Solar Temple
- Origins Space Telescope
- Ost (game)
- Ost (surname)
- Ostend–Bruges International Airport
- Outer Space Treaty
- Socialist Workers Organisation (Senegal)
- Soundtrack
- Vulnerability (computing)