Abstract: A rotary rib cotton gin includes a plurality of gin saw blades axially spaced and rotatably mounted in a gin stand. A ginning breast is pivotally mounted on the gin stand and includes a plurality of stationary ribs having a lower end fixed to the ginning breast, and an upper free end disposed between each adjacent gin saw blade when the ginning breast is in the operating position. The ginning breast further includes a rotary rib rotatably mounted in the ginning breast above the free end of the stationary ribs. The rotary rib includes a plurality of axially spaced rotary discs fixably mounted on a rotatable shaft, wherein an end portion of each rotary disc is disposed between each adjacent gin saw blade when the ginning breast is in the operating position.