Atheris mabuensis, the Mount Mabu forest viper, is a species of venomous snake in the family Viperidae. The species is endemic to Mozambique.
During his second reconnaissance visit to Mount Mabu (23–26 January 2006) Dr. Julian Bayliss found a very young forest viper in leaf litter on the floor of closed-canopy wet forest on Mount Mabu at approximately 1000m (3,000feet). On examination in the Port Elizabeth Museum (BayWorld, acronym PEM) herpetological collection by Prof. Bill Branch, the specimen was identified as a member of the genus Atheris, which had never previously been recorded from Mozambique and which, moreover, represented a substantial southern range extension for the genus.