Schiedea adamantis, commonly known as Diamond Head schiedea, is a species of flowering plant in the family Caryophyllaceae, that is endemic to the island of Oʻahu in Hawaii. It inhabits low shrublands on steep slopes along the northwest rim of Diamond Head Crater. Associated plants include nehe (Lipochaeta lobata var. lobata), kāwelu (Eragrostis variabilis), ʻakoko (Euphorbia degeneri), and ʻilima (Sida fallax). There are only about 30 individuals remaining, and they are threatened by habitat loss.