Isothrix barbarabrownae is a recently discovered species of rodent of the spiny rat family Echimyidae. It was discovered in Peru, and is about the same size as a large squirrel, such as a Eurasian red squirrel. It inhabits the Peruvian cloud forest, where it forages for fruit and nuts. It is a nocturnal, climbing rodent which was collected by scientists in 1999, and formally described in 2006. It is brown, with a black-and-white tail.