Abstract: A wrist joint assembly is provided for use with a mechanical manipulator arm for finely positioning an end-effector carried by the wrist joint on the terminal end of the manipulator arm wherein the wrist joint assembly is pivotable about a first axis to produce a yaw motion, a second axis to produce a pitch motion, and a third axis to produce a roll motion, wherein the three axes are mutually perpendicular and have a common point of origin. The wrist joint assembly includes a disk segment affixed to the terminal end of the manipulator arm and a first housing member rotatably carried on the disk segment about the first axis. A second housing member is rotatably carried on the first housing member and a third housing member is rotatably carried on the second housing member whereby the third housing member and the mechanical end-effector carried thereon are moved in the yaw, pitch, and roll motion.