Atacamatitan (meaning "Atacama Desert titan") is a genus of sauropod dinosaur. It is a titanosaur which lived during the late Cretaceous in what is now northern Chile. It is known from the holotype SGO-PV-961, which includes two dorsal vertebrae, caudal vertebrae, ribs, a possible sternum, part of an upper arm, the right femur, and unidentified incomplete bones. This specimen was found in the Tolar Formation. The discovery locality is near Conchi Viejo town, Atacama Desert in Antofagasta Region. It was named by Alexander W.A. Kellner, David Rubilar-Rogers, Alexander Vargas and Mario Suárez in 2011 and the type species is Atacamatitan chilensis. The specific epithet chilensis refers to Chile.
The fossils were announced as "Domeykosaurus" in 2003 (meaning "Domeyko lizard", after 19th century scientist Ignacy Domeyko) but the name was never formally published.