Astaxanthin (AXT, from Greek astakós "lobster" and  xanthine  to Greek ξανθός (xanthós) "yellowish") is a natural, reddish-violet  Dye that goes to  Xanthophyll class of  carotenoids  counts.

Astaxanthin is primarily produced by green algae and is responsible for the red coloring of crustaceans that consume these algae.