MSO
- List of mine warfare vessels of the United States Navy
- Madison Symphony Orchestra
- Manufacturer Statement of Origin
- Maritime security operations
- Mars Science Orbiter
- Martha Stewart Living Omnimedia
- McLaren Automotive
- Melbourne Ska Orchestra
- Melbourne Symphony Orchestra
- Methionine sulfoximine
- Michigan Southern Railroad (1989)
- Milwaukee Symphony Orchestra
- Mind Sports Olympiad
- Mind Sports Organisation
- Missoula Montana Airport
- Monadic second-order logic
- Monroe Symphony Orchestra
- Montreal Symphony Orchestra
- Moston railway station
- Mountain Skies Observatory
- Multiple system operator
- Municipal Services Office (Singapore)
- Murashige and Skoog medium