A variable geometry turbine, particularly for a supercharger turbocompressor of an internal combustion engine, comprising an outer housing forming a spiral inlet channel for an operating fluid, a rotor supported in a rotary manner in the housing, and an annular vaned nozzle of variable geometry interposed radially between the channel and the rotor and comprising a control member moving axially in order to control of the flow of the operating fluid from the channel to the rotor, the control member being formed as an annular piston of a fluid actuator actuated directly by means of a control pressure.