Ani is a ruined and uninhabited medieval Armenian city-site situated in the Turkish province of Kars, beside the border with Armenia. It was once the capital of a medieval Armenian kingdom that covered much of present day Armenia and eastern Turkey. The city is located on a triangular site, visually dramatic and naturally defensive, protected on its eastern side by the ravine of the Akhurian River and on its western side by the Bostanlar or Tzaghkotzadzor valley. The Akhurian is a branch of the Araks River and forms part of the current border between Turkey and Armenia. Called the "City of 1001 Churches", it stood on various trade routes and its many religious buildings, palaces, and fortifications were amongst the most technically and artistically advanced structures in the world.

At its height, Ani had a population of 100,000-200,000 people and was the rival of Constantinople, Baghdad and Cairo. Long ago renowned for its splendor and magnificence, Ani has been abandoned and largely forgotten for centuries.

Armenian chroniclers such as Yeghishe and Ghazar Parpetsi first mentioned Ani in the 5th century AD. They described it as a strong fortress built on a hilltop and a possession of the Armenian Kamsarakan dynasty. The city took its name from the Armenian fortress-city and pagan center of Ani-Kamakh located in the region of Daranaghi in Upper Armenia. Ani was also previously known as Khnamk, although historians are uncertain as to why it was called so. Johann Heinrich Hubschmann, a German philologist and linguist who studied the Armenian language, suggested that the word may have came from the Armenian word "khnamel", an infinitive which means "to take care of".

By the early 9th century the former territories of the Kamsarakans in Arsharunik and Shirak (including Ani) had been incorporated into the territories of the Armenian Bagratuni dynasty. Their leader, Ashot Msaker (Ashot the Meateater) (806-827) was given the title of ishkhan (prince) of Armenia by the Caliphate in 804. The Bagratunis had their first capital at Bagaran, some 40 km south of Ani, before moving it to Shirakavan, some 25 km northeast of Ani, and then transferring it to Kars in the year 929. In 961 king Ashot III (953-977) transferred the capital from Kars to Ani. Ani expanded rapidly during the reign of King Smbat II (977-989). In 992 the Armenian Catholicosate moved its seat to Ani. In the 10th century the population was perhaps 50,000-100,000.By the start of the 11th century the population of Ani was well over 100,000, and its renown was such that it was known as "The city of forty gates" and "The city of a thousand and one churches."

Ani attained the peak of its power during the long reign of King Gagik I (989-1020). After his death his two sons quarrelled over the succession. The eldest son, Hovhannes Smbat (1020-1041), gained control of Ani and his younger brother, Ashot IV (1020-1040), controlled other parts of the Bagratuni kingdom. Hovhannes-Smbat, fearing that the Byzantine Empire would attack his now weakened kingdom, made the Byzantine Emperor Basil his heir. In January 1022, the Catholicos Peter, handed over to Basil II who was wintering with his army in Trebizond a document from Hovhannes-Smbat pledging his kingdom to the emperor in the event of his death. When Hovhannes-Smbat died in 1041, the successor to Basil, Emperor Michael IV claimed sovereignty over Ani. The new king of Ani, Gagik II (1042-1045), opposed this and several Byzantine armies sent to capture Ani were repulsed. However, in 1045, after the capture of Ashot and at the instigation of pro-Byzantine elements amongst its population, Ani surrendered to Byzantine control. A Greek governor was installed in the city.

Ani did not lie along any previously important trade routes, but because of its size, power, and wealth it became an important trading hub. Its primary trading partners were the Byzantine Empire, the Persian Empire, the Arabs, as well as smaller nations in southern Russia and Central Asia.

In 1064 a large Seljuk Turkish army, headed by Sultan Alp Arslan, with the help of the Caucasian Georgians headed by King Bagrat, attacked Ani and after a siege of 25 days they captured the city and slaughtered its population. An account of the sack and massacres in Ani is given by the Arab historian Sibt ibn al-Gawzi, who quotes an eyewitness saying: "The army entered the city, massacred its inhabitants, pillaged and burned it, leaving it in ruins and taking prisoner all those who remained alive. The dead bodies were so many that they blocked the streets; one could not go anywhere without stepping over them. And the number of prisoners was not less than 50,000 souls. I was determined to enter city and see the destruction with my own eyes. I tried to find a street in which I would not have to walk over the corpses; but that was impossible."

In 1072 the Seljuks sold Ani to the Shaddadids, a Muslim Kurdish dynasty. The Shaddadids generally pursued a conciliatory policy towards the city's overwhelmingly Armenian and Christian population and actually married several members of the Bagratid nobility. Whenever the Shaddadid governance became too intolerant, the population would appeal to the Christian kingdom of Georgia for help. The Georgians captured Ani in 1124, 1161 and 1174, each time eventually returning it to the Shaddadids.

In the year 1199 the forces of the Georgian queen Tamar captured Ani and dislodged the Shaddadids, the governorship of the city was given to Armenian generals Zakare and Ivane Zakarids. At Ani, this new dynasty is generally known as the Zakarids, after its founder Zakare, and they considered themselves to be the successors to the Bagratids. Prosperity quickly returned to Ani; its defences were strengthened and many new churches were constructed. Zakare was succeeded by his son Shahanshah.

The Mongols unsuccessfully besieged Ani in 1226, but in 1236 they captured and sacked the city, massacring large numbers of its population. Ani had fallen when Shahanshah was absent. On his return the Zakarids continued to rule Ani, only now as vassals of the Mongols rather than the Georgians. Ani started its gradual but terminal decline during the Mongol period. By the 14th century the city was ruled by a succession of local Turkish dynasties, including the Jalayrids and the Kara Koyunlu (Black Sheep clan) who made Ani their capital. Tamerlane captured Ani in the 1380s. On his death the Kara Koyunlu regained control but transferred their capital to Yerevan. In 1441 the Armenian Catholicosate did the same. The Persian Safavids then ruled Ani until it became part of the Turkish Ottoman Empire in 1579. A small town remained within its walls at least until the middle 17th century, but the site was entirely abandoned by the middle of the 18th century. The depopulation of Ani was paralleled by the depopulation of its rural hinterland as a result of political unrest in the border region during the Ottoman-Iranian wars and a fragmentation of central control by either of the empires.

In 1905-06, archaeological excavations of the church of Saint Gregory of King Gagik were undertaken, headed by Nikolai Marr. In the first half of the 19th century, European travelers discovered Ani for the outside world, publishing their descriptions in academic journals and travel accounts. In 1878 the Kars region, including Ani, was incorporated into the territory of the Russian Empire. In 1892 the first archaeological excavations were conducted at Ani, sponsored by the St. Petersburg Academy of Sciences and supervised by the Russian archaeologist and orientalist Nikolai Marr (1864-1934). Marr's excavations at Ani resumed in 1904 and continued yearly until 1917. Large sectors of the city were professionally excavated, numerous buildings were uncovered and measured, the finds were studied and published in academic journals, guidebooks for the monuments and the museum were written, and the whole site was surveyed for the first time. Emergency repairs were also undertaken on those buildings that were most at risk of collapse. A museum was established to house the tens of thousands of items found during the excavations. This museum was housed in two buildings: the Minuchihr mosque, and a purpose-built stone building.

In 1918, during the latter stages of World War I, the armies of the Ottoman Empire were fighting their way across the territory of the newly declared Republic of Armenia, capturing Kars in April 1918. At Ani, attempts were made to evacuate the artefacts contained in the museum as Turkish soldiers were approaching the site. About 6000 of the most portable items were removed by archaeologist Ashkharbek Kalantar, a participant of Marr's excavation campaigns. At the behest of Joseph Orbeli, the saved items were consolidated into a museum collection; they are currently part of the collection of Yerevan's State Museum of Armenian History. Everything that was left behind was later looted or destroyed. Turkey's surrender at the end of World War I led to the restoration of Ani to Armenian control, but a resumed offensive against the Armenian Republic in 1920 resulted in Turkey's recapture of Ani. In 1921 the signing of the Treaty of Kars formalised the incorporation of the territory containing Ani into the Republic of Turkey.

In May 1921 the Turkish National Assembly issued a command to the commander of the Eastern Front, Kazim Karabekir, ordering that the "monuments of Ani be wiped off the face of the earth". Karabekir records in his memoirs that he replied dismissively to this command, but the wiping-out of all traces of Marr's excavations and building repairs suggests that the command was partially carried out.