What is the largest living species of sea star?

The sunflower sea star is the largest living sea star species.

Sunflower sea stars, Solaster dawsoni, can reach roughly 1 metre across and have as many as 24 arms. They occur in the northeastern Pacific Ocean, from the intertidal zone to deeper coastal waters. Their many flexible arms and hundreds of tube feet allow them to move rapidly for a sea star.

They are active predators that eat sea urchins, clams, snails, and other invertebrates. A sunflower sea star can extend its stomach outside its body to begin digesting prey before pulling the food inward, a feeding method shared by many sea stars.

The species suffered severe declines during the 2010s because of sea star wasting disease, which caused lesions and tissue breakdown. “Starfish” is a familiar name, but “sea star” is preferred because these animals are not fish.