角龙科（Ceratopsidae）属于头饰龙类，是一群多样性的演化支，例如：三角龙、戟龙。所有已知物种都为四足草食性恐龙，都拥有喙状嘴、颌部后方有多排切割用牙齿、以及延长的头盾与颈盾缘骨突。角龙科可分为两亚科。角龙亚科，或称开角龙亚科，共通特征为长、三角形的头盾，以及发展良好的额部角状物。尖角龙亚科有发展良好的鼻角或鼻部突起物，头盾较短、较呈直角，以及头饰后方的延长针状物。大部分角龙科化石都发现于北美洲西部的上白垩纪地层，只有图兰角龙与中国角龙的化石发现于亚洲。

角龙科的角状物与头盾显示出值得注意的变化，而且是辨别不同物种的主要方式。它们的用途并不完全明确。其中一个用途是抵抗掠食者，但许多物种的头饰是相对易碎的；但更有可能是作为第二性征或物种内竞争用，如同现代的有蹄类。厚鼻龙与河神龙头颅骨上的巨大突起物，类似现代麝牛的突起物，显示牠们可能以头互相碰撞。尖角龙亚科经常与少数其他物种一起以大量化石方式发现，显示这些动物可能是大量群居的动物。

Ceratopsidae (sometimes spelled Ceratopidae) is a speciose group of marginocephalian dinosaurs including Triceratops and Styracosaurus. All known species were quadrupedal herbivores from the Upper Cretaceous, mainly of Western North America (though Sinoceratops is known from Asia) and are characterized by beaks, rows of shearing teeth in the back of the jaw, and elaborate horns and frills. The group is divided into two subfamilies. The Ceratopsinae or Chasmosaurinae are generally characterized by long, triangular frills and well-developed brow horns. The Centrosaurinae had well-developed nasal horns or nasal bosses, shorter and more rectangular frills, and elaborate spines on the back of the frill.