The invention concerns a nozzle (1) adaptable to the steam outlet of a coffee machine designed to froth a liquid, said nozzle is made in one single piece and comprises: an opening (3) for steam supply, a restriction (4) in the extension of said opening; and a flared zone (5) in the axis of said restriction and said opening providing an outlet for the liquid, having a cross-section substantially equal to the cross-section of the opening; and perpendicular to the opening a conduit (2) for supply of the liquid and an air inlet (40).