Sauria is a clade of reptiles that includes all living diapsids, as well as their common ancestor and all its extinct descendants. It was defined by Jacques Gauthier, Arnold G. Kluge and Timothy Rowe (1988) as the group containing the most recent common ancestor of archosaurs and lepidosaurs and all its descendants; a different definition was formulated by Michael deBraga and Olivier Rieppel (1997) who defined Sauria as the clade containing the most recent common ancestor of Choristodera, Archosauromorpha and Lepidosauromorpha and all their descendants. The ancestral saurian was probably a small lizard-like creature living in the Permian Period. This crown group is diagnosed by a number of details in skull and skeleton, and comprises the two important clades Lepidosauromorpha and Archosauromorpha.
The name "Sauria" was coined by James Macartney (1802); it was the Latinisation of the French name Sauriens, coined by Alexandre Brongniart (1800) for an order of reptiles in the classification proposed by the author, containing lizards and crocodilians, later discovered not to be each other's closest relatives. Later authors used the term "Sauria" in a more restricted sense, i.e. as a synonym of Lacertilia, a suborder of Squamata that includes all lizards but excludes snakes. This classification is rarely used today because Sauria so-defined is a paraphyletic group.