The valve comprises: a body (2) through which the fluid flows; and a controllable rotary closure means (3) disposed in the body, which can be rotated in relation to the body in order to occupy different angular positions. Advantageously, the body (2) comprises an inner cylindrical housing (4) having a circular cross-section, and the closure means (3) comprises one portion (14) arranged on a plane inclined in relation to the cylindrical housing (4) and co-operating with the side wall (5) of the housing by means of a peripheral generatrix, such as to provide a sealed contact between the closure means (3) and the body (2) in at least one angular position.