IBU is a three-letter initialism that may refer to:
- Ibuprofen, sold by Par Pharmaceutical under the brand 'IBU'
- International Bitterness Units scale, a measure of the bitterness of beer
- International Biathlon Union, the international organisation for the sport of biathlon
- International Boxing Union (First Version), major boxing sanctioning body, founded 1913, became the European Boxing Union in 1946
- International Boxing Union (Second Version), minor boxing sanctioning body founded in 1996, unconnected with earlier version
- Inshore Boat Unit, a deployable force of 50-100 personnel of the United States Navy who engage in Naval Coastal Warfare
- International Burch University, a university in Sarajevo, Bosnia and Herzegovina
- Ancient Egyptian burial rituals and protocol "Tent of Purification" (ibu, old Egyptian: jbw oder jbw n w'b)
For the Subud figure "Ibu", see Siti Rahayu Wiryohudoyo.