FI, Fi or fi may refer to:
- Falkland Islands, a British Overseas Territory
- Financial Institution
- Finansinspektionen, the Financial Supervisory Authority in Sweden
- Finland (ISO country code, FI)
- Finnish language (ISO 639 alpha-2, fi)
- .fi (top-level domain of Finland)
- The abbreviation for Firenze, the Italian province of Florence
- The IATA code for Icelandair (from the old name of the company: Flugfélag Íslands)
- Forza Italia, an Italian political party
- Franciscans International, an NGO at the United Nations
- Functional Integration, an individual lesson in the Feldenkrais method
- The Fourth International
- The Feminist Initiative (Sweden)
- The album fi (album) by Bibio
- A scripting command in the Bourne shell and its derivatives (bash)
- fi (fi) a common typographical ligature
- Forced induction
- Fuel injection
- Fast Infoset, a standard for binary XML Infoset encoding.
- Fi (Star Wars), a Star Wars Expanded Universe character
- A diminutive of the feminine given name Fiona
- The pitch equivalent to the fourth scale degree raised a half step in modern Solfège
- Fi (The Legend of Zelda), a character in the video game The Legend of Zelda: Skyward Sword