Alania was a medieval kingdom of the Iranian Alans (Proto-Ossetians) that flourished between the 9th–13th centuries in the Northern Caucasus, roughly in the location of the latter-day Circassia, South Ossetia, Chechnya, Ingushetia, and modern North Ossetia–Alania. With its capital at Maghas, the location of which is still disputed, it became independent from the Khazars in the late 9th century. It was Christianized by a Byzantine missionary soon after, in the early 10th century.

Reaching its peak in the 11th century, under the rule of King Durgulel, it profited from controlling a vital trade route through the Darial Pass. It maintained close relations not only with the Byzantine Empire but also the Kingdom of Georgia, as well as the small Dagestani kingdom of Sarir; the first two also employed Alan mercenaries, who were infamous horsemen. It was responsible for spreading Orthodox Christianity among neighbouring pagan peoples such as the Circassians and Vainakhs. The kingdom eventually declined from the 12th century and had largely ceased to function as a political entity by the early 13th century. In 1239/1240 the Mongols invaded, stormed and destroyed the capital, Maghas, in the process.

The name Alania derives from the Old Iranian stem *Aryāna-, a derivative form of the Indo-Iranian stem *arya- ('Aryan'). It is cognate with the name of Iran (Ērān), which stems from the Old Persian *Aryānām ('of the Aryans').

In other sources, they are mentioned as “Ās”. In Russian chronicles and Hungarian sources they are called “Yas”.

The Caucasian Alans occupied part of the Caucasian plain and the foothills of the main mountain chain from the headwaters of the Kuban river and its tributary, Zelenchuk in the west, to the Darial Gorge in the east. In the 10th century the Arab historian al-Masʿūdī indicates that the Alan kingdom stretched from Daghestan to Abkhazia. According to Ḥudūd al-ʿĀlam, In the north, the Alans bordered on the Hungarians and the Bulgars. In the east they gave their name to the Darial Gorge, called "Gate of the Alans". Before the Mongol invasion, the Alans lived in the territory from the Laba River to the Argun.

According to al-Masʿūdī, the Alan ruler was powerful and influential among the neighboring rulers being able to muster 30,000 horsemen. He also said "The Alan kingdom consisted of an uninterrupted series of settlements; when the cock crows (in one of them), the answer comes from the other parts of the kingdom, because the villages are intermingled and close together." According to Ḥudūd al-ʿĀlam, Alania is described as a vast country with 1,000 settlements. The population consisted of both Christians and Pagans, mountaineers and nomads.

The Alans (Alani) originated as an Iranian-speaking subdivision of the Sarmatians. They were split by the invasion of the Huns into two parts, the European and the Caucasian. The Caucasian Alans occupied part of the North Caucasian plain and the foothills of the main mountain chain from the headwaters of the Kuban River in the west to the Darial Gorge in the east.

Alania was an important buffer state during the Byzantine-Arab Wars and Khazar-Arab Wars of the 8th century. Theophanes the Confessor left a detailed account of Leo the Isaurian's mission to Alania in the early 8th century. Leo was instructed by Emperor Justinian II to bribe the Alan leader Itaxes into severing his "ancient friendship" with the Kingdom of Abkhazia, which had allied itself with Caliph Al-Walid I. He crossed the mountain passes and concluded an alliance with the Alans, but was prevented from returning to Byzantium through Abasgia. Although the Abkhazians spared no expense to have him imprisoned, the Alans refused to convey the Byzantine envoy to his enemies. After several months of adventures in the Northern Caucasus, Leo extricated himself from the precarious situation and returned to Constantinople.