Plug-in connector, comprising - a plug-in connector housing having multiple sides, each having a flat form, - a plug insert which is fixed or at least can be fixed in the plug-in connector housing, and - a releasing sleeve which engages around the plug-in connector housing and is held on said plug-in connector housing such that it is displaceable in the opposite direction to the plug-in direction, and - at least one locking and releasing element which is arranged between a first side of the plug-in connector housing and the releasing sleeve, wherein the locking and releasing element is held on the plug-in connector housing, wherein the locking and releasing element is formed at least in part from a spring-elastic material in order to thereby ensure its ability to move, and wherein the locking and releasing element has two latching arms, wherein each latching arm has a first and a second end and wherein each latching arm is attached by way of its first end to the plug-in connector housing, characterized in that the locking and releasing element, at least in regions, is moveable parallel to the first side, wherein the second end of each latching arm is movable parallel to said first side of the plug-in connector housing, in that the latching arms are held on the plug-in connector housing such that they are moveable in opposite directions to one another, and in that the releasing sleeve has, on a broad side wall, two releasing pins for interacting with a respective engagement device arranged on each of the two latching arms, wherein the engagement device is an integrally formed portion with a contact bevel which interacts with a releasing pin of the releasing sleeve, so that the two latching arms are pulled apart from one another by their respective engagement devices as soon as the releasing sleeve is pulled in the opposite direction to the plug-in direction. - a plug-in connector housing having multiple sides, each having a flat form, - a plug insert which is fixed or at least can be fixed in the plug-in connector housing, and - a releasing sleeve which engages around the plug-in connector housing and is held on said plug-in connector housing such that it is displaceable in the opposite direction to the plug-in direction, and - at least one locking and releasing element which is arranged between a first side of the plug-in connector housing and the releasing sleeve, wherein the locking and releasing element is held on the plug-in connector housing, wherein the locking and releasing element is formed at least in part from a spring-elastic material in order to thereby ensure its ability to move, and wherein the locking and releasing element has two latching arms, wherein each latching arm has a first and a second end and wherein each latching arm is attached by way of its first end to the plug-in connector housing, characterized in that the locking and releasing element, at least in regions, is moveable parallel to the first side, wherein the second end of each latching arm is movable parallel to said first side of the plug-in connector housing, in that the latching arms are held on the plug-in connector housing such that they are moveable in opposite directions to one another, and in that the releasing sleeve has, on a broad side wall, two releasing pins for interacting with a respective engagement device arranged on each of the two latching arms, wherein the engagement device is an integrally formed portion with a contact bevel which interacts with a releasing pin of the releasing sleeve, so that the two latching arms are pulled apart from one another by their respective engagement devices as soon as the releasing sleeve is pulled in the opposite direction to the plug-in direction.