Control valve

This disclosure reliably causes transition to a locked state at the time of internal combustion engine deactivation and reliably causes transition to the locked state when a locking mechanism is not in the locked state at the time of internal combustion engine activation. A control valve spool is operable to a phase control position in which the supply/discharge of a fluid to/from an advance port and a retard port is controlled while the fluid is supplied to a lock releasing port, and to a lock transition position in which the supply/discharge of the fluid to/from the advance port and the retard port is controlled while the fluid is discharged from the lock releasing port. A communication path through which a portion of the fluid from a pump port is discharged to a drain port when the spool is operated to the lock transition position is formed.