Astaxanthin is a naturally occurring keto-carotenoid pigment and potent antioxidant belonging to the xanthophyll class. It is biosynthesized by microalgae such as Haematococcus pluvialis and accumulates in marine animals including salmon, krill, and shrimp, imparting their characteristic pink-red coloration. Structurally, it features conjugated double bonds with keto and hydroxy groups at the 4,4' and 3,3' positions, enabling strong free-radical scavenging. Research demonstrates benefits for reducing oxidative stress, supporting eye and skin health, modulating inflammation, and enhancing mitochondrial function. It is widely used in dietary supplements, functional foods, and aquaculture feeds, with GRAS status from the FDA for specified uses.