Abstract: The present invention is an improved quick release locking nut for quick change type mop holders. The mop holder has a frame attachable to a mop stick and a clamping member for securing mop fill. The quick release locking nut is slidably mounted on a central shank of the frame, and has a pivotally mounted pawl which is biased by a spring. The inner screw threads on the tip of the pawl are engaged with the outer screw threads on the central shank, in order to lock the quick release locking nut on the central shank for preventing the clamping member from sliding on the central shank. When the pawl is pressed against the spring and its tip is disengaged from the central shank, the quick release locking nut is unlocked and can be slid on the central shank for allowing the clamping member to slide on the central shank so that the mop clamp can be released.