Lewisuchus is a genus of archosaur that lived during the Late Triassic (early Carnian). As a silesaurid dinosauriform, it was a member of the group of reptiles most commonly considered to be the closest relatives of dinosaurs (possibly true dinosaurs themselves). Lewisuchus was about 1 metre (3.3 ft) long. Fossils have been found in the Chañares Formation of Argentina. It exhibited osteoderms along its back.