Abstract: An eccentrically rotatable control valve having a spherical shaped valve plug is positioned in a valve chamber to regulate the flow of fluid there through. The valve plug is retained in a loosely captured position by means of a bolt and spring to the end of a valve actuating arm for flexible, swivel movement thereon. This construction enables the plug to be initially rotated from a completely open position into line contact with a part of the valve seat in the wall of the chamber, and to then be jointly tilted and rolled about this seat part into and out of fluid tight surface to surface contact with the entire valve seat. The plug and arm are mounted on and for limited longitudinal movement with an associated valve actuator shaft that extends through the chamber. The latter construction provides a means by which the plug can center itself in a properly seated fluid tight position on the seat in the event that the valve seat is out of properly aligned seating surface engagement with the plug.