Abstract: A firing pin safety mechanism for a weapon such as a pistol. An inertia firing pin is provided with an annular groove. The firing pin is spring loaded in the firing pin channel of the pistol slide. The safety is provided with a rib canted toward the hammer side of the firing pin. The safety is slidable between "on" and "off" positions within a safety channel which intersects the firing pin channel. When the safety is moved to the "on" position, the rib enters the firing pin groove and cams the firing pin so as to retract and lock the pin in a sheathed position within the slide. In the sheathed position, the firing pin can neither contact the cartridge nor be contacted by the weapon hammer. When the safety is moved to the "off" position, the rib clears the firing pin, and the hammer end of the firing pin is exposed. The firing pin is then free to be operated by the weapon hammer to strike the cartridge.