Astropecten armatus, the spiny sand star or Estrella de Arena, is a sea star in the family Astropectinidae. It is found on sandy or gravelly areas in the East Pacific ranging from California (USA) to Ecuador.

Description Astropecten armatus is a dorsally flattened starfish, which grows to a diameter of about 17 cm (7 in). The disc is quite small and the five arms are slender and pointed, slightly turned up at the tips. The madreporite is very close to the edge of the disc. The central surface of both disc and arms is smooth. The arms have conspicuous marginal plates with a fringe of upward pointing spines and another of downward pointing ones. Further rows of spines line the ambulacral grooves. The tube feet are pointed and do not have suckers. The colour of the aboral (upper) surface is yellowish brown, dull pink or grey and the starfish blends in well with the colour of the substrate.