Abstract: The valve comprises a valve body defining a valve chamber having input and output openings, and housing a rotatable shutter element, traversed by a passage, adapted for selectively connecting the input and output openings. Provided between at least one of the openings and the shutter element, is a sealing seat having a truncated-cone shape with its axis lying in a plane, substantially perpendicular to the axis of rotation of the shutter element and inclined with respect to the axis of the opening. The sealing seat has, in a plane which is perpendicular to the axis of the opening an ellipse portion, placed eccentrically with respect to the axis of the opening, with the eccentricity arranged along the major axis of the ellipse on the part which is opposite with respect to the position of the apex of the cone relatively to the axis of the opening. On the shutter element, a sealing ring is provided, for engagement with the sealing seat upon closing the valve.