IFN of IfN may mean
- Interferon, a type of signaling proteins
- Integrated Flux Nebula, a cloud of gas and dust illuminated by the integrated flux of all the stars in the Milky Way (rather than a single star or group of stars).
- Leibniz Institute for Neurobiology (Leibniz-Institut für Neurobiologie), Germany
- India Fund, Inc., a mutual fund
- Isfahan International Airport (IATA code)
- Institutet för Näringslivsforskning, Research Institute for Industrial Economics, Sweden
- Instituto di Fotonica e Nanotecnologie, Institute for Photonics and Nanotechnologies, Trento, Italy