Epimedium grandiflorum, the large flowered barrenwort, or bishop's hat, is a species of flowering plant in the family Berberidaceae, native to Japan and Korea.
It is a deciduous perennial growing to , with bright red stems with green heart-shaped leaves (copper-tinged when young) which are slightly hairy on the bottom. In spring it produces pink, white, yellow or purple long-spurred flowers. The Latin specific epithet grandiflorum means large-flowered.
Numerous cultivars have been selected for garden use, of which the following have gained the Royal Horticultural Society's Award of Garden Merit:
It is commonly packed in a capsule with other ingredients or sold as herbal flakes or powder with the name "horny goat weed".