SSO may refer to:
- Iran's Social Security Organization (SSO)
- Statistical Society of Ottawa, the Ottawa Regional Association of the Statistical Society of Canada and the Ottawa Chapter of the American Statistical Association.
- Sanitary sewer overflow
- Senior Station Officer, a rank in the New Zealand Fire Service
- Structure, sequence and organization, a concept in copyright law
- Special Security Office, is a function of the US federal government and armed forces
- Special Security Officers, a group of people with law Enforcement
- Single sign-on, a system designed to minimize the number of times that a user must log into multiple applications
- Special Security Organization (Iraqi)
- Sso (rite), an initiation rite once practised by the Beti of Cameroon
- Standards Setting Organization, an organization promulgating or maintaining standards
- Sydney Star Observer, a newspaper in Sydney, Australia
- Super Surgical Operation
- Swiss Space Office, space agency of Switzerland
- Siding Spring Observatory
- Student Switch Off, a UK-based energy saving campaign
In fiction:
- Starship Operators, a TV sci-fi anime series
- UMF/SSO-3 ASH, a battlesuit in the anime Gundam
In music:
- Salford Symphony Orchestra
- Saskatoon Symphony Orchestra
- Scottish Symphony Orchestra
- Seattle Symphony Orchestra
- Shreveport Symphony Orchestra
- Singapore Symphony Orchestra
- Springfield Symphony Orchestra
- Sudbury Symphony Orchestra
- Sun Symphony Orchestra
- Sydney Symphony Orchestra
- Syracuse Symphony Orchestra
In spaceflight:
- Scaled Composites SpaceShipOne, the vehicle used in the first ever privately funded human spaceflight
- Semi-synchronous orbit, a type of Earth orbit
- single-stage-to-orbit, a vehicle that reaches orbit without jettisoning hardware
- Space Shuttle Orbiter, an orbital spaceplane operated by NASA
- Sun-synchronous orbit, a type of Earth orbit