| Named By: | C. Navarrete, G. Casal & R. Martinez in 2008 |
| Time Period: | Upper Cretaceous, Cenomanian-Turonian |
| Location: | Argentina, Santa Cruz Province - Bajo Barreal Formation |
| Size: | Unavailable |
| Diet: | Herbivore |
| Fossil(s): | Partial post cranial skeleton |
| Classification: | | Chordata | Reptilia | Dinosauria | Saurischia | Sauropoda | Titanosauria | Lognkosauria | |
Drusilasaura is an extinct genus of possible lognkosaurian titanosaur sauropod dinosaur which lived during the late Cretaceous (Cenomanian-Turonian stage) of Santa Cruz Province of southern Patagonia, Argentina.
Drusilasaura is known from the holotype MPM-PV 2097/1 to 2097/19, a partial skeleton including four dorsal vertebrae, a sacral vertebra, six caudal vertebrae, a left scapula, dorsal rib fragments and other fragments. It was found by palaeontologist Marcelo Tejedor searching fossil mammals, in layers of the Upper Member of the Bajo Barreal Formation, on the Maria Aike Ranch owned by the Ortiz de Zarate family. A team from the Laboratorio de Paleontologia de Vertebrados of the Universidad Nacional de la Patagonia San Juan Bosco subsequently collected the remains.
Drusilasaura was named by Cesar Navarrete, Gabriel Casal and Ruben Martinez in 2011. The type species is Drusilasaura deseadensis. The generic name honours Drusila Ortiz de Zarate, a young female member of the family, also occasioning the choice of the feminine form ~saura. The specific name refers to the Rio Deseado.
Drusilasaura is a large sauropod. The length of the scapula is 143 centimetres, 30% longer than that of Mendozasaurus.
Drusilasaura was assigned to the Titanosauridae by the describers and considered a possible member of the Lognkosauria. If so, it would be the oldest known lognkosaurian.