Brain is the industry standard name for a computer virus that was released in its first form on 19 January 1986, and is considered to be the first computer virus for the IBM Personal Computer and compatibles.

A computer virus is a type of malware that, when executed, replicates itself by modifying other computer programs and inserting its own code into those programs. If this replication succeeds, the affected areas are then said to be "infected" with a computer virus, a metaphor derived from biological viruses.