Prometheus is an inner satellite of Saturn. It was discovered on 24 October 1980 from photos taken by the Voyager 1 probe, and was provisionally designated S/1980 S 27.

In astronomy, an inner moon or inner natural satellite is a natural satellite following a prograde, low-inclination orbit inwards of the large satellites of the parent planet. They are generally thought to have been formed in situ at the same time as the coalescence of the original planet. Neptune's moons are an exception, as they are likely reaggregates of the pieces of the original bodies, which were disrupted after the capture of the large moon Triton. Inner satellites are distinguished from other regular satellites by their proximity to the parent planet, their short orbital periods, their low mass, small size, and irregular shapes.