Romneya coulteri, the Coulter's Matilija poppy or California tree poppy, is a species of flowering plant in the poppy family. Native to southern California and Baja California, it grows in dry canyons in chaparral and coastal sage scrub plant communities, sometimes in areas recently burned. It is a popular ornamental plant, kept for its large, showy flowers. The specific epithet commemorates Thomas Coulter, an Irish botanist and explorer.