- ACOI stands for American College of Osteopathic Internists
- ACOI stands for Associazione Chirurghi Ospedalieri Italiani (Italian: National Congress of Italian Hospital Surgeons; Italy)
- ACOI stands for Association of Compliance Officers in Ireland (est. 2002)
- ACOI stands for Army Court of Inquiry (India)
- ACOI stands for American College of Oral Implantologists
ACOI