The saola, Vu Quang ox or Asian unicorn, also, infrequently, Vu Quang bovid (Pseudoryx nghetinhensis), one of the world's rarest mammals, is a forest-dwelling bovine found only in the Annamite Range of Vietnam and Laos. The species was defined following a discovery of remains in 1992 in Vu Quang Nature Reserve by a joint survey of the Ministry of Forestry and the World Wide Fund for Nature. The team found three skulls with unusual long straight horns kept in hunters' houses. In their article, the team proposed "a three month survey to observe the living animal" but, more than 20 years later, there is still no reported sighting of a saola in the wild by a scientist.

In late August 2010, a saola was captured by villagers in Laos but died in captivity before government conservationists could arrange for it to be released back in to the wild. The carcass is being studied with the hope that it will advance scientific understanding of the saola.

The saola inhabits the Annamite Range's moist forests and the Eastern Indochina dry and monsoon forests. They have been spotted in steep river valleys at about 300 to 1800 m above sea level. These regions are distant from human settlements, covered primarily in evergreen or mixed evergreen and deciduous woodlands. The species seems to prefer edge zones of the forests.