IAA
- Academia Sinica Institute of Astronomy and Astrophysics
- Auxin
- D.I.C.E. Awards
- Grand Theft Auto V
- Id al Adha
- Idyllwild Arts Academy
- Igarka Airport
- Illinois Agricultural Association
- Imidazole-4-acetic acid
- Immigration Appellate Authority
- Independent Ambulance Association
- Indian Association of Alberta
- Indianapolis Airport Authority
- Indole-3-acetic acid
- Inflammatory aortic aneurysm
- Information Affairs Authority
- Institute for Applied Autonomy
- Instituto Antártico Argentino
- Instituto de Arqueología Amazónica
- Instituto de Astrofísica de Andalucía
- Insulin autoantibody
- Intelligence Authorization Act
- Inter-American Academy of Guayaquil
- Interlochen Center for the Arts
- International Academy of Architecture
- International Academy of Astronautics
- International Actuarial Association
- International Advertising Association
- International Ammunition Association
- International Astrostatistics Association
- International Motor Show Germany
- Interrupted aortic arch
- Iodoacetamide
- Iran Aseman Airlines
- Irish Aviation Authority
- Islamic Army of Aden
- Isoamyl alcohol
- Israel Airports Authority
- Israel Antiquities Authority
- Israeli Astronomical Association
- National Collegiate Athletic Association