Plug-in coupling with two interlocking tubular coupling parts

A plug-in coupling with two tubular coupling parts (1, 2) that can be plugged together to connect two fluid-carrying components has a first annular groove (13) in an insertion section (14) of one coupling part (2) and in a receiving section (6) of the other coupling part (1) two diametrically opposite slots (12) and an approximately U-shaped elastic retaining bracket (3). The legs (15) of the bracket project through the slots (12) and snap into the first annular groove (13) when the coupling parts (1, 2) are plugged together. The plug-in coupling furthermore has a sealing ring (4) between the plugged-together coupling parts (1, 2) and a locking ring (5) which, together with the one coupling part (1) and a shoulder (31) of this coupling part (1), defines a second annular groove (32) receiving the sealing ring (4). In order to achieve an axially shortest possible plug-in area of the receiving and insertion sections (6, 14), the receiving section (6) has a radially outer peripheral wall (10) and a radially inner peripheral wall (11), wherein the inner peripheral wall (11) has on its radially outer peripheral side the second annular groove (32) at least approximately in the same radial plane as the first annular groove (13).