Fluid coupling system

A fluid coupling system (1) for vehicles configured to be attached to the chassis (V) of vehicles, comprising a male connecting element (2), a female connecting element (3) and a retaining bolt (4), the male element (2) comprising at least one axial section configured for insertion into a housing of the female element (3), both said elements (2, 3) comprising pass-through openings (20, 30) that coincide with respect to a common axial axis (X), the female element comprising (3) an opening (31) that crosses the housing orthogonally to the axial axis (X) but at a distance from same, the male element (2) comprising at least one grooved neck (21) in at least one of the axial sections to be inserted into the female element (3), said neck (21) and said opening (31) being configured to receive the bolt (4) in its condition of use, characterised in that said bolt contains an elastic ring (7) seated in a circumferential groove close to the end of the bolt (4).