Abstract: An improved, large diameter butterfly valve specially adapted for use in corrosive or high temperature environments. The valve closure plate of the butterfly valve includes a frame comprised of a shaft, an annular flat bar defining the perimeter of the frame and lightweight stringers extending from the shaft to the flat bar. An elastomeric material is formed around the peripheral portion of the flat bar to provide a sealing flange extending radially outwardly from the periphery of the frame. Balsa filler panels are disposed between the stringers and extend from the shaft to the flat bar. The exterior of the valve closure plate is formed by a shell of glass fiber reinforced resin laid over and adhered to the frame and the balsa filler panels. The elastomeric sealing flange extends radially outwardly beyond the resin exterior shell so as to contact a seat on the housing of the butterfly valve when the closure plate is in a closed position, thereby forming a fluid tight seal.