Dario Fo, Italian playwright and Nobel laureate

First-order logic, a system of mathematical logic

Abbreviation for Fuck Off

Faroe Islands (country code FO)

Fuel oil

Number 4 (slang abbreviation fo’)

XSL Formatting Objects (XSL-FO)

Abbreviation for the computer game Fallout (computer game)

Frame optional military symbol

Faroese language (language code fo)

Forward Observer, a soldier who directs artillery fire

Football Outsiders, a website devoted to statistical analysis of the NFL

Forum, an online communications medium

Foreign and Commonwealth Office of the British government

FO, a subunit of F1FO type ATPase

Foreign object

Force Ouvrière, a French trade unions confederation

Flying Officer, a Royal Air Force rank

Airlines of Tasmania IATA airline designator

Furka-Oberalp-Bahn, a Swiss railway

Field officer, a senior army officer

Fourier number (Fo) in physics

Face Off

Foreign Objects, a Pennsylvania music group

Fo, one of the 9 departments of the Houet Province of Burkina Faso.