The buckthorns are two closely related genera (formerly often treated together as one genus) of shrubs or small trees in the family Rhamnaceae; the name is also often applied to the family as a whole:
Rhamnaceae Rhamnus Frangula
Buckthorn, often hyphenated, may also refer to: Hippophae rhamnoides (sea-buckthorn) Sideroxylon lanuginosum (false buckthorn or wooly buckthorn)