Abstract: A rotary steam engine comprising a hollow cylindrical housing, a cylindrical rotor mounted concentrically within the housing having radially extending vanes rigidly secured thereto projecting between the rotor and the housing to form chambers therebetween in conjunction with the rotor and housing, a plurality of rotary valves carried in the housing and spaced angularly around the periphery of the rotor in rolling engagement with the rotor and having pockets therein for receiving the vanes as they pass through the valves, a gear train for synchronizing the rotation of the rotor and valves, means for passing fluid into the chambers between the rotor and housing and exhausting fluid therefrom positioned adjacent each of the valves, a rotation selector plate for porting the fluid under pressure into and exhausting the fluid from the chambers for selecting direction of rotation of the rotor, and a separate cutoff plate associated with each of the valves synchronized with the rotation of the valves for shutting off