Electrical plug-in connector which can be connected to one end of an electrical line or a cable, wherein the end to be connected has at least one free wire end, and wherein the plug-in connector is to be connected to a plug-in connector complementary to the plug-in connector along a longitudinal axis, comprising the following features: - a contact support; - at least one contact element which is inserted in the contact support in parallel with this longitudinal axis and is held thereby in a supporting manner, wherein the contact element has a front and a rear end (31, 32), and wherein the rear end has a clamping spring with a clamping opening in which the at least one free wire end can be clamped; - a housing part which is assembled on the contact support and has an inner surface which at least partially surrounds the clamping spring after assembly; a contact opener, in particular an elongate contact opener, which is to be allocated to the clamping spring, is arranged at least partially between this inner surface and the clamping spring and, after assembly, is held so as to be movable between two positions; wherein a first movement is a pulling movement of the contact opener along the longitudinal axis, which occurs in the viewing direction of the rear end of the contact element, and a second movement is a pushing movement of the contact opener along the longitudinal axis which occurs in the viewing direction of the front end of the contact element; wherein the inner surface forms a region in which at least one part of the contact opener is accommodated in a first position of the contact opener so that the clamping spring is released; characterised in that - a surface oriented at least partially transverse to the longitudinal axis is formed in each case on this inner surface and on a side of the contact opener facing this inner surface, whereby in order to actuate the clamping spring along the longitudinal direction, the contact opener can be moved by a first sliding movement on the surface of this inner surface oriented transverse to the longitudinal axis from the first position in which the clamping spring is released to a second position in which the contact opener compresses the clamping spring so that the clamping opening is opened for insertion or removal of this free wire end, and the contact opener can be moved back towards the first position blocking the clamping opening by a second sliding movement on the surface of this inner surface oriented transverse to the longitudinal axis. - a contact support; - at least one contact element which is inserted in the contact support in parallel with this longitudinal axis and is held thereby in a supporting manner, wherein the contact element has a front and a rear end (31, 32), and wherein the rear end has a clamping spring with a clamping opening in which the at least one free wire end can be clamped; - a housing part which is assembled on the contact support and has an inner surface which at least partially surrounds the clamping spring after assembly; a contact opener, in particular an elongate contact opener, which is to be allocated to the clamping spring, is arranged at least partially between this inner surface and the clamping spring and, after assembly, is held so as to be movable between two positions; wherein a first movement is a pulling movement of the contact opener along the longitudinal axis, which occurs in the viewing direction of the rear end of the contact element, and a second movement is a pushing movement of the contact opener along the longitudinal axis which occurs in the viewing direction of the front end of the contact element; wherein the inner surface forms a region in which at least one part of the contact opener is accommodated in a first position of the contact opener so that the clamping spring is released; characterised in that - a surface oriented at least partially transverse to the longitudinal axis is formed in each case on this inner surface and on a side of the contact opener facing this inner surface, whereby in order to actuate the clamping spring along the longitudinal direction, the contact opener can be moved by a first sliding movement on the surface of this inner surface oriented transverse to the longitudinal axis from the first position in which the clamping spring is released to a second position in which the contact opener compresses the clamping spring so that the clamping opening is opened for insertion or removal of this free wire end, and the contact opener can be moved back towards the first position blocking the clamping opening by a second sliding movement on the surface of this inner surface oriented transverse to the longitudinal axis.