Fluid line plug-in coupling, at least having a coupling housing, having a substantially U-shaped holding clip, which has two spring legs (3B, 3C) and a connecting arch, wherein the holding clip is arranged in a through-passage of the coupling housing in such a way that the spring legs (3B, 3C) project at least partially into the interior of the coupling housing in a holding position of the holding clip, and having a coupling connector, which can be pushed into the coupling housing and has at least one coding lug (9, 10) and one collar, wherein, with the coupling connector plugged in, the spring legs (3B, 3C) of the holding clip are snapped in behind the collar of the coupling connector in the holding position of the holding clip, characterized in that - the coupling housing has on its outer surface in the region of the through-passage of the coupling housing two run-on bevels (2B, 2C) which are arranged in such a way that the spring legs (3B, 3C) come to lie with their ends (4B, 4C) in the region of the run-on bevels (2B, 2C) in a starting position, in which the holding clip is displaced radially outwards, - wherein, in this state, the spring legs (3B, 3C) are spread radially outwards beyond their holding position, wherein a spring-back force can be generated in the spring legs (3B, 3C) of the holding clip, which spring force makes it possible for the holding clip to slide back into the holding position automatically, - the automatic sliding-back of the holding clip into the holding position can be prevented by a latch which has a first and a second step (5B, 5C) and which is arranged so as to be axially displaceable in the coupling housing, - wherein, in its first position, its starting position, the latch engages with its first step below the connecting arch of the holding clip, and in this way the sliding-back of the holding clip into the holding position is not possible, and, - during the pushing into the coupling housing, the coding lug of the coupling connector is guided towards the latch, whereby, during the pushing-in of the coupling connector, the latch can be displaced from its starting position into a normal position, - in which the latch releases the connecting arch with its second step, the radial thickness of which second step is smaller than that of the first step, such that the holding clip can be positioned automatically into its holding position by way of the spring-back force such that the holding clip snaps in behind the collar of the coupling connector and the coupling connector is consequently secured against axial pulling-apart against the coupling housing. - the coupling housing has on its outer surface in the region of the through-passage of the coupling housing two run-on bevels (2B, 2C) which are arranged in such a way that the spring legs (3B, 3C) come to lie with their ends (4B, 4C) in the region of the run-on bevels (2B, 2C) in a starting position, in which the holding clip is displaced radially outwards, - wherein, in this state, the spring legs (3B, 3C) are spread radially outwards beyond their holding position, wherein a spring-back force can be generated in the spring legs (3B, 3C) of the holding clip, which spring force makes it possible for the holding clip to slide back into the holding position automatically, - the automatic sliding-back of the holding clip into the holding position can be prevented by a latch which has a first and a second step (5B, 5C) and which is arranged so as to be axially displaceable in the coupling housing, - wherein, in its first position, its starting position, the latch engages with its first step below the connecting arch of the holding clip, and in this way the sliding-back of the holding clip into the holding position is not possible, and, - during the pushing into the coupling housing, the coding lug of the coupling connector is guided towards the latch, whereby, during the pushing-in of the coupling connector, the latch can be displaced from its starting position into a normal position, - in which the latch releases the connecting arch with its second step, the radial thickness of which second step is smaller than that of the first step, such that the holding clip can be positioned automatically into its holding position by way of the spring-back force such that the holding clip snaps in behind the collar of the coupling connector and the coupling connector is consequently secured against axial pulling-apart against the coupling housing.