FIN may refer to
- the ISO 3166-1 alpha-3-code for Finland.
- a Financial Accounting Standards Board FASB Interpretation Number.
- Federazione Italiana Nuoto, the Italian Swimming Federation.
- A FIN packet in the Transmission Control Protocol (TCP).
- The Internationalist League of Norway (Norwegian: Forbundet Internasjonalen i Noreg)
- Collar number, aka Force Identification Number, a four-character code used to identify uniformed police officers.
