The Nilgiri tahr', Nilgiritragus hylocrius, known locally as the Nilgiri ibex or simply ibex, is an ungulate that is endemic to the Nilgiri Hills and the southern portion of the Western Ghats in the states of Tamil Nadu and Kerala in southern India. It is the state animal of Tamil Nadu. Despite its local name, it is more closely related to the sheep of the Ovis genus than the ibex and wild goats of the Capra genus.

In the Tamil Language it is called varaiaadu, the term being composed of two Tamil words, wurrai a precipice, and aadu, a goat. It is also the state animal of Tamil Nadu. It was previously named Capra warryato by Gray.

Its closest relatives are sheep (genus Ovis). Until 2005, it was placed with the Himalayan tahr (Hemitragus jemlahicus) and the Arabian tahr (Arabitragus jayakari) in the genus Hemitragus. However, it has recently been transferred to a new genus Nilgiritragus because it is genetically more similar to members of the genus Ovis than to other tahrs.

The Nilgiri tahrs are stocky goats with short, coarse fur and a bristly mane. Males are larger than the females, and have a darker color when mature. Both sexes have curved horns, which are larger in the males, reaching up to 40 centimetres (16 in) for males and 30 centimetres (12 in) for females. Adult males weigh 80 to 100 kilograms (180 to 220 lb) and stand about 100 centimetres (39 in) tall at the shoulder. Adult males develop a light grey area on their backs and are thus called "saddlebacks".