Doria's tree-kangaroo, also known as Doria's tree-wallaby, is a rare species of arboreal marsupial found in the rainforests of New Guinea. It is a small to medium-sized kangaroo with soft grey fur, a long tail, and powerful hind legs. It is an elusive animal with no close relatives, and therefore, has no widely accepted synonyms. However, some common informal synonyms for Doria's tree-kangaroo include tree-wallaby, tree kangaroo, and gray tree kangaroo. Despite being rare, this unique animal is a critical component of the ecosystem and requires urgent conservation measures to protect it from extinction.