A flow control valve for a filling machine configured to fill receptacles with a pourable product, the flow control valve comprising: a tubular body defining a channel for the pourable product, the tubular body having a longitudinal axis and terminating with at least one narrowed end mouth; and a shutter movable within the channel between a closed position, and an open position. The shutter includes a main portion coupled in a sliding manner with an inner surface of the tubular body; and a narrowed closing head, wherein the main portion of the shutter includes a flat plate extending along a diameter of the channel with respect to the longitudinal axis, contacting the inner surface of the tubular body at opposite sides and defining, with the remaining portions of the inner surface, two opposite cavities, which have respective profiles shaped as circular segments and through which the pourable product can flow during operation.