Boi or BOI may refer to:
Boise (/bɔɪsi/) is the capital and most populous city of the U.S. state of Idaho, as well as the county seat of Ada County.
The boiling water reactor (BWR) is a type of light water nuclear reactor used for the generation of electrical power.
Boise State University (BSU) is a college in Boise, Idaho. Founded in 1932 by the Episcopal Church, it became an independent junior college in 1934, and has been awarding baccalaureate and master's degrees since 1965.
A boiler is a closed vessel in which water or other fluid is heated. The fluid does not necessarily boil.
Boise National Forest is a National Forest covering 2,203,703 acres (8,918.07 km2) of the U.S. state of Idaho.