The Green Sea Urchin (Psammechinus miliaris) is a marine (saltwater) echinoderm in the Parechinidae family. It is also known as the Shore Sea Urchin.

The Green Sea Urchin is spherical-shaped (ball-shaped). Its rounded “body” is called a test. The test is covered with short, thick spines of about the same length. It is purple-brown in shallow water and greenish in deeper water. The spines are a paler colour with purple tips. It has tubed feet in groups of five or six in a small arc shape. It has a small mouth. It does not have eyes. It is sensitive to touch, light, and chemicals due to the numerous sensitive cells in its spines, tube feet, and around its mouth.