Luidia magellanica is a species of starfish in the family Luidiidae. It is found in the southeastern Pacific Ocean on the coast of South America.

Distribution and habitat Luidia magellanica occurs subtidally in the southeastern Pacific Ocean, on the coasts of Peru and Chile. Its typical habitat is on rock bottoms with encrusting red algae, Lithophyllum, or soft sediments composed of coarse sand and shell fragments.

Ecology Luidia magellanica is a large and aggressive specialist predator of other echinoderms. Its diet includes brittle stars such as Ophiactis, sea urchins such as Tetrapygus niger and starfish such as Patiria. In the subtidal zone of temperate Chile it feeds on eight different species of echinoderm, and with Meyenaster gelatinosus is the dominant predator. Many of the starfish in this zone have missing or regenerating arms, and this is likely to be as a result of a near-lethal encounter with either L. magellanica or M. gelatinosus. Both of these species also exhibit cannibalism. When attacked by M. gelatinosus or by a larger member of its own species, L. magellanica tends to autotomise some 4 to 5 cm (1.6 to 2.0 in) of a single arm.