The Rákosi viper (Vipera ursinii rakosiensis) is a subspecies of the imperial viper (Vipera ursinii) belonging to the order of scaly reptiles, the suborder of snakes and the viper family. It is an extremely rare venomous snake, occurring exclusively in Hungary, and is recognized as the most endangered animal in the fauna of the Carpathian Basin. In the course of time - with respect to Mátyás Rákosi - for political reasons (and incorrectly from the point of view of the species) it was also called imperial viper and Rákosréti viper. In the Great Plain, it was called the sand viper, but official science uses this name to designate another species (Vipera ammodytes).