Triceratops is a genus of herbivorous ceratopsid dinosaur that first appeared during the late Maastrichtian stage of the late Cretaceous period, about 68 million years ago (mya) in what is now North America. It is one of the last known non-avian dinosaur genera, and became extinct in the Cretaceous–Paleogene extinction event 66 million years ago. The term Triceratops, which literally means "three-horned face", is derived from the Greek τρί- (tri-) meaning "three", κέρας (kéras) meaning "horn", and ὤψ (ops) meaning "face".
Bearing a large bony frill and three horns on its large four-legged body, and possessing similarities with the modern rhinoceros, Triceratops is one of the most recognizable of all dinosaurs and the best known ceratopsid. It shared the landscape with and was probably preyed upon by Tyrannosaurus, though it is less certain that the two did battle in the manner often depicted in traditional museum displays and popular images.
The exact placement of the genus Triceratops within the ceratopsid group has been debated by paleontologists. Two species, T. horridus and T. prorsus, are considered valid, although many other species have been named. Research published in 2010 suggested that the contemporaneous Torosaurus, a ceratopsid long regarded as a separate genus, represents Triceratops in its mature form. The view was immediately disputed and examination of more fossil evidence is expected to settle the debate.