Abstract: A reversible latch bolt assembly for a mortise lock. The latch bolt assembly generally comprises a bolt head subassembly having a stem threaded into the rear. The bolt head subassembly engages body designed for anchoring the reversible latch bolt assembly inside a door. The stem is inserted distally into an aperture in the body. A rotary selector assembly is mounted in the body orthogonal to the stem aperture and, when the stem is inserted, selectively engages or disengages the collar of the stem to prevent or allow rotation thereof. The rotary selector assembly is spring biased toward a normally locked position but is rotated to an unlocked position by a hex key or the like. The selector assembly allows free rotation of the bolt head when necessary to reverse the mortise lock, depending on whether the lock is mounted in a left-hand or right-hand door. Since the integral selector assembly is key-operative from the latch body tampering is much more difficult.