RS Puppis (or RS Pup) is a Cepheid variable star in the constellation of Puppis. It is one of the brightest known Cepheids in the Milky Way galaxyand has one of the longest periods for this class of star, of 41.4^[8] days.

Because it is located in a large nebula, astronomers using the ESO‘s New Technology Telescope at La Silla Observatory, Chile have been able to measure its distance in 2013 by strictly geometric analysis of light echoes from particles in the nebula, determining it to be 6500 ± 90 light years from Earth, the most accurate measurement achieved for any Cepheid as of early 2008. The accuracy of the new measurement is important because Cepheids serve as a marker for distances within the Milky Way galaxy and for nearby galaxies.