Gamatavus (meaning "Picada do Gama great-grandfather") is a genus of silesaurid dinosauriform from the Middle Triassic Santa Maria Formation of Dilermando de Aguiar Municipality, Brazil.

The Gamatavus holotype specimen, UFSM 11348a, was discovered in the Dinodontosaurus Assemblage Zone of the Santa Maria Formation (‘Picada do Gama’ site), dated to the Ladinian–early Carnian stages of the Middle Triassic.

The generic name, "Gamatavus", combines a reference to the type locality (Picada do Gama site) with the Latin word "atavus", meaning "great-grandfather".

[1] Topology 1: Ezcurra et al. (2020) dataset Lagosuchus Lutungutali Lewisuchus Silesaurus Asilisaurus Gamatavus Ornithischia Saurischia

Topology 2: Müller and Garcia (2020) dataset Lagosuchus Lewisuchus Asilisaurus Soumyasaurus Technosaurus Sacisaurus Diodorus Gamatavus Lutungutali Kwanasaurus Ignotosaurus Silesaurus Eucoelophysis Pisanosaurus core Ornithischia Saurischia