The invention relates to a sleeper for the track superstructure, which is manufactured in one piece from a plastic material, with the sleeper having an elongated base shape with two end sections, which are connected by a middle section of the sleeper and held at a distance and on their upper side in each case one contact surface is provided for in each case one rail to be supported on the respective end section with a reinforcement extending in the longitudinal direction of the sleeper being embedded into the middle section. In order to design such a plastic sleeper such that it has optimised strength and can be reliably manufactured even using cost-effective plastic/sand mixtures having a high proportion of sand, the invention proposes that the reinforcement extends over the length of the middle section, that the reinforcement is in each case anchored in the respective end section an edge region of the end sections assigned to the middle section and in that the reinforcement is wholly or partially arranged in the upper quarter of the height of the sleeper.