- Institutional review board, a committee that reviews the designs of proposed experiments to confirm whether all the methods proposed are ethical. (more: Institutional review board at Wikipedia)
- Investment review board, a committee of business executives who review investment choices, comparing against strategy and opportunity costs.
- Internal review board, another name for an internal affairs division of a police department (more: Internal affairs (law enforcement) at Wikipedia)
- Internal-ratings-based approach.
- Irish Republican Brotherhood, a secret organisation dedicated to the establishment of an "independent democratic republic" in Ireland between 1858 and 1924.
- (rugby, historical usage) International Rugby Board, the name used by World Rugby, the worldwide governing body for rugby union, from 1998 to 2014.