FSO may refer to:
Government Federal Protective Service (Russia) (Russian: ), responsible for the security of Russian state officials Federal Statistical Office (Switzerland) Financial Secretary's Office, of the Government of Hong Kong Foreign Service Officer, of the United States Foreign Service Forest Section Officer, in India
Music Fairfax Symphony Orchestra, in Virginia, United States Frankston Symphony Orchestra, in Victoria, Australia Fulham Symphony Orchestra, in London "F.S.O.", the first single from the Regurgitator album Tu-Plang Film Symphony Orchestra, Czech classical orchestra
Transport Fabryka Samochodów Osobowych, a Polish automotive company Franklin County State Airport, in Vermont, United States Subiaco railway station, in Western Australia
Other uses Fire Support Officer Flash shared object Floating storage and offloading Free-space optical communication Flag Service Organization