Abstract: A pop-up rotor type irrigation sprinkler has a pivotable butterfly valve body located in its riser just below the nozzle. The valve body is selectively pivotable between fully open and fully closed positions by manually turning a drive member mounted in the upper end of the riser with a hand tool. The drive member is connected to the valve body with a linkage that extends within the riser outside of the water flow path to avoid adversely affecting the water stream ejected from the nozzle. The valve body has an elliptical shape and is curved in section and downwardly concave when in its closed position. Due to its curved shape, the valve body can pivot to its vertical open position in which it rests parallel with the curved cylindrical interior wall of an internal flow tube to minimize flow resistance.