FDN may refer to:
- Fixed Dialing Number
- Dolphin Air, whose ICAO code is FDN
- Nicaraguan Democratic Force, Fuerza Democrática Nicaragüense (FDN)
- Fairbanks Daily News-Miner, a newspaper in Fairbanks, Alaska
- FdN/fPcN - Freunde der Naturvölker, German section of the international indigenous rights organization, Friends of Peoples Close to Nature
- "Fecha de Nacimiento", Spanish for Date of Birth (FdN / DoB)
- Abbreviation for "foundation" in English.
- Functional Diagnostic Nutrition, a holistic health-related approach to chronic disease diagnosis and an associated professional certification.
- French Data Network, a non-profit ISP operating mainly in France.