genus of spring-flowering perennial herbs of the family Melanthiaceae, consisting of about 25 species, native to North America and Asia. They have oval leaves in whorls of three at the top of the stem. The flower parts and fruits also are in threes.

Each solitary white, greenish white, yellow, pink, or purple flower is borne on a short stalk that arises from the whorl of leaves. Many species of Trillium are cultivated in wildflower gardens.