原蜥形目（Prolacertiformes）又名原龙类（Protorosauria），属于双孔亚纲的主龙形下纲，生存在二叠纪与三叠纪。许多物种已演化成树栖生活，包括有三角形翼的滑翔动物沙洛维龙；其他如长颈龙，拥有长而疆直的颈部，可能用来捕抓鱼类，可能是部分水生动物。

其他了解不多的爬行动物，有时会被研究人员归类到原蜥形目，包括：镰龙科（Drepanosauridae）、长鳞龙、翼龙目。在2004年，菲力·森特（Phil Senter）将奇特的树栖动物－镰龙科、长鳞龙，重新归类到鸟首龙目（Avicephala），此目为更原始的双孔动物，但有些研究人员仍将这些动物归类于原蜥形目。

Protorosauria is an extinct group of archosauromorph reptiles from the latest Permian (Changhsingian stage) to the early Late Triassic (Carnian stage) of Asia, Europe, North America. It was named by the English anatomist and paleontologist Thomas Henry Huxley in 1871 as an order. Other names that are for the most part equivalent to Protorosauria include Prolacertiformes and Prolacertilia. Protorosaurs are distinguished by their long necks formed by elongated cervical vertebrae, which have ribs that extend backward to the vertebrae behind them. Protorosaurs also have a gap between the quadrate bones and the jugal bones in the back of the skull near the jaw joint, making their skulls resemble those of lizards.