OCB may refer to:
- OCB mode, a mode of operation for cryptographic block ciphers
- Oil circuit breaker, a form of circuit breaker using oil as an insulating medium
- Oklahoma City bombing, a bomb attack on the Alfred P. Murrah Federal Building in downtown Oklahoma City on April 19, 1995
- Old Country Buffet, a chain of restaurants managed by Buffets, Inc.
- Operations Coordinating Board (1953—1961), a committee of the United States Executive
- Óquei Clube de Barcelos, a rink hockey team from Barcelos, Portugal
- Orange Catholic Bible, a fictional book from the Dune universe created by Frank Herbert
- Organizational citizenship behavior, a special type of work behavior
- Ordinary course of business, a term in law covering the usual transactions, customs and practices of a certain business and of a certain firm
- Orient Commercial Joint Stock Bank (OCB), a large bank located in Vietnam