An insert coupling more preferably intended for use with fuel lines consists of a sleeve-like coupling body (2) and a tubular insert part (1) carrying a retaining rib (3) on the outside. Via a coupling element (22) axially fixed in the coupling body (2) on to which engagement hooks (4, 4′) are molded which are intended for engagement with the retaining rib (3), a ring shoulder (23) is formed at the same time which together with a ring shoulder (24) of the housing (8) of the coupling body (2) axially spaced from said ring shoulder and the radially spaced cylindrical faces of the housing (8) facing each other and the insert part (1) define a ring space (11) in which a sealing arrangement consisting of two sealing rings (5, 7) and a support ring (6) arranged in-between are accommodated. As a result of the unambiguous axial fixing of the sealing arrangement in the housing (8) the function of the sealing arrangement is not impaired through the removal of the insert part (1) from the coupling body (2) and through inserting said insert part in the coupling body (2). A simple construction of the insert coupling is obtained in that said coupling factually consists only of three substantial components plus the sealing arrangement and can be employed with insert parts (1) which are smooth-walled except for a retaining rib (3).