A rotating disk of gas and dust around a young counterpart to β Pictoris

β Pictoris is the best known example of a main-sequence star encircled by a tenuous disk. Optical and infrared images of β Pic suggest that the disk is composed of dust grains which have been interpreted as the debris generated by the disruption of the asteroid-sized remnants of planet- formation processes. The star itself is relatively old, with an age in excess of 100 Myr. Here we present high-resolution millimetre-wave images of continuum and molecular-line emission from dust and gas surrounding a much younger star, MWC480: the stellar properties of MWC480 are similar to those of β Pic, but its age is just 6 Myr. The morphology of the circumstellar material and a comparison with the predictions of kinematic modelling indicate the presence of a rotating disk, gravitationally bound to the star. Moreover, the mass of the disk is greater than the minimum required to form a planetary system like our own. We therefore suggest that the disk around the young star MWC480 could be a progenitor of debris disks of the type associated with older stars such as β Pic, and so holds much promise for the study of both the origin of debris disks and the early stages of the formation of planetary systems.