Fib may refer to:
- Fib (poetry), a form of poetry similar to haiku
- Fib, a Pictish kingdom, which went on to become Fife, in modern Scotland
- Fibonacci number, for which Fib is a common abbreviation, used in computer programming.
- A fib or fibbing, a type of deception; an untruth.
FIB is an acronym or abbreviation that may mean one of the following:
- Facultat d'Informàtica de Barcelona, the Barcelona School of Informatics of the Technical University of Catalonia
- Fill in the Blank, a type of question.
- Focused ion beam, an analytical instrument used in the semiconductor industry
- Federation of International Bandy, the international governing body for the sport of bandy
- Festival Internacional de Benicàssim, a music festival held in Benicàssim, Castelló, Spain
- Fédération Internationale de Boules - International bocce federation
- The gene encoding fibrinogen
- Forwarding Information Base
- Federal Investigation Bureau, an Austrian federal police force
- Federal Investigation Bureau, a fictional agency in the 2008 video game Grand Theft Auto IV, based on the real life Federal Bureau of Investigation (FBI)
- Folket i Bild (FiB, "people in pictures") was a Swedish illustrated news magazine (1933-1963) owned by the Swedish Social Democratic Party. After it was sold to a commercial publisher in 1963, the name changed to FIB Aktuellt and it was remade into a gentlemen's magazine, gradually turning into pornography. As a reaction, the leftist-political Folket i Bild/Kulturfront (FiB/K) was founded in 1972.
- Fricking Illinois Bastard- A derogatory term for citizens of the state of Illinois, predominately used by the citizens of Wisconsin, especially in the Milwaukee area.