蜥蜴，是对属于有鳞目蜥蜴亚目的物种的总称。

蜥蜴是爬虫类中种类最多的族群，目前全世界已知超过4000种，主要分布于热带地区。体型差异很大，从数公分大的加勒比壁虎，到近3公尺长的科莫多龙都有。

有些被称为蛇蜥的种类脚已经退化，只留下一些脚的痕迹构造；牠们因为有眼睑和耳朵，所以能与蛇区分。

许多蜥蜴能变换牠们的颜色以因应环境的变化或压力，例如变色龙。

大部分的种类为肉食性，以昆虫、蚯蚓、蜗牛，甚至老鼠等为食。但也有以仙人掌或海藻为主食，或是杂食性的。

Lizards are a widespread group of squamate reptiles, with approximately over 6,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group, traditionally recognized as the suborder Lacertilia, is defined as all extant members of the Lepidosauria (reptiles with overlapping scales) that are neither sphenodonts (i.e., tuatara) nor snakes – they form an evolutionary grade. While the snakes are recognized as falling phylogenetically within the Toxicofera clade from which they evolved, the sphenodonts are the sister group to the squamates, the larger monophyletic group, which includes both the lizards and the snakes.