Abstract: A pneumatic pipe plug for the sealing of pipelines of various nominal diameters can be inserted through connections of relatively small diameters in a wall of a pipeline and is intended for high working and dynamic pressures in order to ascertain good sealing, whereat the plug is also conceived in a way to be resistant to mechanical damages that could occur when inserting the plug into or removing it from a connection in the wall, said connection being often sharp-edged. The pipe plug of the invention is conceived as a tube element (1) in the sense of an ellipsoid of revolution, whereat the thickness of a wall (8) of the element (1) becomes thinner towards the centre and the wall can also contain a gummed cord (9) running in several, preferably two layers so that, with respect to the longitudinal axis of the element (1), one cord (9) lies obliquely to one end and another cord (9) to another end for an angle a measured from the central line and amounting to 0-20° C.