The giant tree-rat (Toromys grandis ) is a species in the family Echimyidae, the spiny rats. It is the only species in the monotypic genus Toromys. It is endemic to Brazil, where it occurs in the flooded forest along the banks of the Amazon River and its tributaries.
This species was formerly considered to be a member of the genera Loncheres and Makalata. In 2005 it was reclassified as the only member of the new genus Toromys.
The etymology of the genus name derives from the onomatopoeic Portuguese word toró, referring to the vocalizations of this rodent, and the ancient greek word μῦς (mûs ), meaning "mouse, rat".
