A pistol including a mechanism that locks firing pin of the pistol. The firing pin locking mechanism may include a stopping member which may be selectively moved by a user of the pistol between first and second positions, and a movable blocking member that may be engaged with a forwardly-movable firing pin. A biasing member such as a spring may be provided to bias the blocking member into engagement with the firing pin. In one embodiment, the blocking member arrests or blocks the forward motion of the firing pin to prevent the firing pin from striking a loaded cartridge and discharging the pistol. In a possible first activated position, the stopping member prevents the firing pin blocking member from being operably disengaged from the firing pin, thereby preventing the firing pin from moving forward to strike a cartridge. In a possible second deactivated position, the stopping member allows the firing pin blocking member to be disengaged from the firing pin by normal operation of the pistol trigger system to allow the pistol to be discharged. The firing pin locking mechanism may further include a locking member to allow a pistol user to lock the stopping member in the first position or second position.