An actuator for a butterfly valve, having a gearbox, an actuator stem and a handle. The actuator stem is formed as a single piece, comprising a position indicator, seal disc, worm gear, and stem shaft with splines for fitting into the valve. The handle is also formed as a single piece, comprising the wheel or knob, shaft, and worm for operating the worm gear. By forming the gearbox as a single piece as well, the entire actuator can be made as three major pieces. Optionally, the gearbox can be formed with cylindrical fittings which press-fit over pins on the valve, replacing the conventional mounting bracket.