The quick coupling for fluid under pressure, comprising a hollow valve body, an obturator stem slidable along an axis of the valve body in contrast and by the action of elastic means configured and arranged to automatically arrange said obturator stem in a closing position of the valve body, and hydraulic sealing means between the valve body and a cylindrical terminal of the obturator stem, the hydraulic sealing means comprising at least one hollow plain bearing for reducing friction having an internal cylindrical surface mateable with the terminal of the obturator stem, and a plurality of elastic elements independent from one another configured and arranged to strain the bearing at a radial compression force for the uniform hydraulic seal against the terminal, the elastic elements being distributed at least mainly along the extension of the bearing in the direction of the axis.