A turbomachine including at least one unducted propeller with variable pitch blades, the blades being carried by respective plates mounted to pivot in radial housings of a rotor element and connected to a control ring that is driven in rotation about the axis of the turbomachine together with the rotor element, and that is movable in translation along the axis to pivot the plates about their axes, the control ring being centered and guided in rotation about the axis on a mechanism that is stationary in rotation and movable in translation along the axis by an actuator carried by the stator of the turbomachine.