FI or fi may refer to:

• Falkland Islands, a British Overseas Territory
• Finland (ISO country code FI)
  • Finnish language (ISO 639 alpha-2 code "fi")
  • .fi, top-level domain of Finland
• Province of Firenze, Italy

• fi (album), a 2005 album by Bibio
• Fi (TV series), a 2017 Turkish Internet TV series
• Fi (The Legend of Zelda), a character in the 2011 video game The Legend of Zelda: Skyward Sword
• Fi, the pitch equivalent to the fourth scale degree raised a half step, in the Solfège music education method
• Films Incorporated a defunct educational movie company abbreviated to FI

• Feminist Initiative (Sweden), a political party
• Finansinspektionen, the Financial Supervisory Authority in Sweden
• Forza Italia, an Italian political party
• Fourth International, an international communist organisation
• Franciscans International, an NGO at the United Nations
• Freudenthal Institute, a research institute that is part of Utrecht University
• Front de l'Indépendance, a Belgian resistance organization in World War II
• Icelandair (IATA code FI, from the old name of the company, Flugfélag Íslands)
• La France Insoumise, a French political party
• Financial Institution, establishment that focuses on the financial and/or monetary sector

• fi, a scripting command in the Bourne shell and its derivatives
• Fast Infoset, a standard for binary XML Infoset encoding
• Fuel injection, a system for introducing fuel into internal combustion engines
• High fidelity (disambiguation) (hi-fi)
• Lo-fi (disambiguation)
• Google Fi Wireless, a mobile virtual network operated by Google

• fi (fi), a typographical ligature
• Fecal incontinence
• Fi (letter), a Georgian letter
• Fiona Hammond (born 1983), Australian water polo player nicknamed "Fi"

• "Fee-fi-fo-fum", the first line of an historical quatrain (or sometimes couplet) famous for its use in the classic English fairy tale "Jack and the Beanstalk"
• FEI (disambiguation)
• Fie (disambiguation)
• Phi (Φ), a letter of the Greek alphabet