A motorized ball valve comprising: a ball valve assembly including a valve housing having an inlet for receiving fluid, an outlet for discharging fluid, a flow channel connecting the inlet and outlet, and a controllable ball element moveable to selectively vary the cross-sectional area of flow of at least a portion of the flow channel; and a stand-alone ball valve actuator mounted on the ball valve assembly and comprising: a hermetically sealable actuator housing including a valve interface configured for releasably coupling the stand-alone ball valve actuator to the ball valve assembly; an electric motor arranged in the actuator housing, configured to selectively rotate the ball element of the ball valve assembly via a gearing and a coupling member; an encoder assembly for producing a position signal representative of the rotational position of the coupling member; a transceiver system arranged in the actuator housing for wirelessly receiving configuration information regarding a desired rotational position of the coupling member; a processor arranged in the actuator housing configured to process said position signal and said configuration information, and control the electric motor to rotate the ball element, accordingly, and a self-contained power source arranged in the actuator housing for driving the processor, the transceiver system and the electric motor, characterized in that the valve interface includes a releasable stem connection for connecting the coupling member to a stem of the ball valve assembly; wherein the stem connection is arranged inside the actuator housing in a position retracted from a bottom face of the actuator housing constituting part of the valve interface. a ball valve assembly including a valve housing having an inlet for receiving fluid, an outlet for discharging fluid, a flow channel connecting the inlet and outlet, and a controllable ball element moveable to selectively vary the cross-sectional area of flow of at least a portion of the flow channel; and a stand-alone ball valve actuator mounted on the ball valve assembly and comprising: a hermetically sealable actuator housing including a valve interface configured for releasably coupling the stand-alone ball valve actuator to the ball valve assembly; an electric motor arranged in the actuator housing, configured to selectively rotate the ball element of the ball valve assembly via a gearing and a coupling member; an encoder assembly for producing a position signal representative of the rotational position of the coupling member; a transceiver system arranged in the actuator housing for wirelessly receiving configuration information regarding a desired rotational position of the coupling member; a processor arranged in the actuator housing configured to process said position signal and said configuration information, and control the electric motor to rotate the ball element, accordingly, and a self-contained power source arranged in the actuator housing for driving the processor, the transceiver system and the electric motor, characterized in that the valve interface includes a releasable stem connection for connecting the coupling member to a stem of the ball valve assembly; wherein the stem connection is arranged inside the actuator housing in a position retracted from a bottom face of the actuator housing constituting part of the valve interface. a hermetically sealable actuator housing including a valve interface configured for releasably coupling the stand-alone ball valve actuator to the ball valve assembly; an electric motor arranged in the actuator housing, configured to selectively rotate the ball element of the ball valve assembly via a gearing and a coupling member; an encoder assembly for producing a position signal representative of the rotational position of the coupling member; a transceiver system arranged in the actuator housing for wirelessly receiving configuration information regarding a desired rotational position of the coupling member; a processor arranged in the actuator housing configured to process said position signal and said configuration information, and control the electric motor to rotate the ball element, accordingly, and a self-contained power source arranged in the actuator housing for driving the processor, the transceiver system and the electric motor, characterized in that the valve interface includes a releasable stem connection for connecting the coupling member to a stem of the ball valve assembly; wherein the stem connection is arranged inside the actuator housing in a position retracted from a bottom face of the actuator housing constituting part of the valve interface.