The Nubian ibex (Capra nubiana) is a desert-dwelling goat species (Genus Capra) found in mountainous areas of northern and northeast Africa, and the Middle East. It was historically considered to be a subspecies of the Alpine ibex (C. ibex), but is now considered a distinct species. The wild population is estimated at 4,500 mature individuals, and it is classified as vulnerable.

The Nubian ibex was first identified in modern science by Frédéric Cuvier in his 1825 Histoire naturelle des mammifères: avec des figures originales, coloriées, dessinées d'aprèsdes animaux vivans, in which he illustrated the animal with the label "Bouc sauvage de la Haute-Égypte" ("Wild goat of Upper Egypt"). It was initially classified as Capra ibex nubiana, a subspecies of the Alpine ibex (C. ibex), which had been previously identified by Carl Linnaeus in 1758. Other early researchers classified it as a now-defunct synonym, C. sinaitica, or the Sinai ibex. While it was referred to as its own species, C. nubiana, by some authors in the 19th and early 20th Century, the first widely recognized researcher to classify the Nubian ibex as a unique species, and not as a subspecies, was Hans-Peter Uerpmann in his 1987 book, The ancient distribution of ungulate mammals in the Middle East: fauna and archaeological sites in Southwest Asia and Northeast Africa. Capra nubiana, the Nubian ibex, is now broadly accepted by scientists as a unique species.

The earliest remains of the Nubian ibex in the Palestine region date back approximately 150,000 years to the Pleistocene, and it has been continually present in the region since then. In spite of the growing presence of livestock like domesticated goats over the last 10,000 years, Nubian ibex in the region have remained present throughout this time. However, its abundance has fluctuated over time in places like Ein Gedi, where it showed an increase in population in the Late Holocene between approximately 5,165 and 950 years ago. Radiocarbon dated bones from archaeological excavations indicate that the Nubian ibex has been in a predator-prey relationship with the Arabian leopard throughout the Holocene.

The Nubian ibex shares a genus, Capra, with all other ibex and goats. Phylogenetic reconstructions of the ibex/goat family tree have mixed results, with different studies reaching different conclusions.

One Y-chromosomal DNA analysis suggests two clades (subgroups) within the genus: The first clade contains domestic goats (C. hircus), wild goats (C. aegagrus), and markhors (C. falconeri). The second clade contains all other ibex, including the Nubian ibex. In this analysis, the Nubian ibex is monophyletic (most closely related) to the Siberian ibex (C. sibirica).

However, when the same study analyzed Mitochondrial DNA, it was suggested that all species in genus Capra are in one clade except for the Siberian ibex. The study's authors provide potential explanations for this discrepancy, including a possible ancient hybridization of the ancestors of the two Y-chromosome clades.

A separate mitochondrial study suggests that the Nubian ibex forms a separate, more ancient offshoot from most other ibex and may be monophyletic with the Siberian ibex.

An additional Y-chromosomal DNA and mitochondrial DNA study concludes that Nubian ibex are most closely related to Ethiopia's Walia ibex (C. walie), and they may have separated about 800,000 years ago.