原角龙科（Protoceratopsidae）是角龙下目恐龙的一科，名称在希腊文的意思为“第一种脸上有角的”。牠们在外表上类似血缘关系极接近的角龙科，但通常体型较小、较为原始。到目前为止，原角龙科都在晚白垩纪的亚洲耐梅盖特组发现，地质年代相当于9960万到7060万年前模式属是原角龙。

原角龙科是在1923年由沃特·格兰杰（Walter W. Granger）与威廉·葛莱谷瑞（William K. Gregory）创建，当时只有单一种安氏原角龙（Protoceratops andrewsi）。Granger与Gregory认为原角龙血缘与其他角龙类接近，但因为够原始可独立成立一科，甚至可成立亚目。稍晚，原角龙科的范围扩张为：所有比鹦鹉嘴龙科先进，而比角龙科原始的角龙类。在1998年，保罗·塞里诺（Paul Sereno）将原角龙科定义为：所有血缘接近原角龙，而较三角龙远的冠饰角龙类所构成的基群演化支。塞里诺的定义使原角龙科成为单系群，但可能不包含某些传统上被认为是原角龙科的恐龙，例如纤角龙、蒙大拿角龙。以上两者现在常被分类于纤角龙科，该科大部分发现于北美洲。

Protoceratopsidae is a family within the group Ceratopsia. The name Protoceratopsid is derived from Greek for "first horned face". Protoceratopsids have so far been found exclusively in the Late Cretaceous, dating to between about 99.6 and 70.6 million years ago. Although Ceratopsians have been found all over the world, Protoceratopsids lived only in Asia with most specimens found in China and the Nemegt Basin in Mongolia. Like most Ceratopsians, Protoceratopsids were herbivorous, with blocks of teeth made for grinding that were constantly being replaced and a hooked beak for grabbing plants. Protoceratopsids were relatively small, between 1-2.5 m in length from head to tail. Their bony frill and horns were much smaller than the related Ceratopsids. Protoceratopsids were likely slow runners and tended to move at a walk or a trot. Their legs may have been vertical, but there are some theories that they were splayed out to the side, contributing to their slowness. There is evidence that Protoceratops formed aggregations. Specimens of juveniles and young adults are often found in groups, although adults tend to be solitary. The nature of these groups is not completely known, though herds of young likely formed for protection from predators, and adults are believed to have come together for communal nesting.