MSO may refer to:
Chemistry
- Methionine sulfoximine, a chemical compound that inhibits glutamine synthetase irreversibly
Orchestras
- Madison Symphony Orchestra, of Madison, Wisconsin, USA
- Melbourne Symphony Orchestra, of Melbourne, Victoria, Australia
- Milwaukee Symphony Orchestra, of Milwaukee, Wisconsin, USA
- Montreal Symphony Orchestra, of Montreal, Quebec, Canada
- Metropolitan Symphony Orchestra, of Natick, Massachusetts, USA
Companies and organizations
- Martha Stewart Living Omnimedia, a merchandising company founded by Martha Stewart
- Management Services Officer, the departmental head of administrative staff within the Academic Administration of a US university
- Management Services Organization, a term for a legal entity that provides management and administrative services to other organizations
- McLaren Special Operations, McLaren's bespoke division
- Michigan Southern Railroad (1989), a wholly owned subsidiary of Pioneer Railcorp
- Mind Sports Organization, a vehicle for promoting mental-skill games
- Muslim Students Organisation of India, a students and youth wing of Sunni Muslims.
- Mixed Service Organisation, displaced persons employed by the British Army on the Rhine in various positions up until the end of the Cold War
Telecommunications
- Multiple system operator, a class of cable television service provider
Other uses
- A file format used by the Microsoft Outlook e-mail application
- Maritime Security Operations, a method of policing various illegal activities at sea
- Manufacturer Statement of Origin, a document of ownership, usually related to a motor vehicle
- Mind Sports Olympiad, a multi-discipline international tournament for mind sports
- Missoula International Airport, public airport located in Montana, USA (IATA code: MSO)
- Mountain Skies Observatory, an astronomical observatory Wyoming, USA
- Murashige and Skoog medium, a plant growth medium used in laboratories for cellular cultivation
- United States Navy hull code for "ocean minesweeper," a type of Minesweeper (ship)
- Moston railway station, a railway station in Greater Manchester, England (National Rail code: MSO)
- Mixed-signal oscilloscope
- Mars Science Orbiter, a proposed spacraft to be sent to Mars
- Monadic second-order logic, a higher-order logic