A lockable safety selector switch adapted to replace a manufacturer's original safety selector switch for a firearm having a selector detent pin with a tip. The lockable safety selector switch has a body adapted to selectively orient between a SAFE position that prevents the firearm from firing and a FIRE position that allows the firearm to fire, and a locking mechanism configured to operatively associate with the firearm selector detent pin to selectively lock the body in the SAFE position. The locking mechanism has a spring-loaded cam that operatively interfaces with a key to prevent unintentional locking or unlocking of the locking mechanism. The locking mechanism is operated by a key adapted to operate a handcuff lock. The lockable safety selector switch is configured such that the firearm requires no modification for the lockable safety selector switch to replace the original safety selector switch.