Hanger chain anti-sway device for gantry crane

A sway dampener is provided for reducing sway motion of a gantry crane spreader that is suspended from hanger chains. The sway dampener is configured to resist motion of the hanger chain relative to the spreader, thereby retarding sway. The dampener includes first and second portions that are movable relative to each other in a resistive fashion, for example a piston-cylinder structure. The first portion is mounted to the spreader and the second portion is mounted to the hanger chain at an attachment point located a vertical distance above a point at which the hanger chain is pivotally mounted to the spreader so that horizontal sway motion of the attachment point relative to the spreader displaces the first and second portions.