The Nakhchivan Autonomous Republic (Azerbaijani: Naxçıvan Muxtar Respublikası, pronounced [nɑxtʃɯˈvɑn muxˈtɑɾ ɾesˈpublikɑsɯ]) is a landlocked exclave of the Republic of Azerbaijan. The region covers 5,502.75 km² (2,124.62 sq mi) with a population of 459,600. It is bordered by Armenia to the east and north, Iran to the southwest, and Turkey to the west. It is the sole autonomous republic of Azerbaijan, governed by its own elected legislature.

The republic, especially the capital city of Nakhchivan, has a long history dating back to about 1500 BC. Nakhijevan was one the cantons of the historical Armenian province of Vaspurakan in the Kingdom of Armenia. Historically, the Persians, Armenians, Mongols, and Turks all competed for the region. The area that is now Nakhchivan became part of Safavid Iran in the 16th century. The semi-autonomous Nakhchivan Khanate was established there in the mid-18th century. In 1828, after the last Russo-Persian War and the Treaty of Turkmenchay, the Nakhchivan Khanate passed from Iranian into Imperial Russian possession.

After the 1917 February Revolution, Nakhchivan and its surrounding region were under the authority of the Special Transcaucasian Committee of the Russian Provisional Government and subsequently of the short-lived Transcaucasian Democratic Federative Republic. When the TDFR was dissolved in May 1918, Nakhchivan, Nagorno-Karabakh, Syunik, and Qazakh were heavily contested between the newly formed and short-lived states of the First Republic of Armenia and the Azerbaijan Democratic Republic (ADR). In June 1918, the region came under Ottoman occupation. Under the terms of the Armistice of Mudros, the Ottomans agreed to pull their troops out of the Transcaucasus to make way for British occupation at the close of the First World War. The British placed Nakhchivan under Armenian administration in April 1919, although an Azerbaijani revolt prevented Armenia from establishing full control over the territory.

In July 1920, the Bolsheviks occupied the region. In November of that year, Bolshevik Russia and Azerbaijan both promised that Nakhchivan, alongside neighboring Nagorno-Karabakh and Zangezur, was an "integral part" of Armenia. However, on March 16, 1921, in accordance with the results of a referendum, the Bolshevik government declared the Nakhchivan Autonomous Soviet Socialist Republic, which went on to become an autonomous republic within the Azerbaijan Soviet Socialist Republic in 1924. In January 1990, Nakhchivan declared independence from the USSR to protest against the suppression of the national movement in Azerbaijan, and became the Nakhchivan Autonomous Republic within the newly independent Republic of Azerbaijan a year later.

Though a mixed Azerbaijani-Armenian region as late as a century ago, Nakhchivan is homogeneously Azerbaijani today besides a small population of Russians.

Variations of the name Nakhchivan include Nakhichevan, Naxcivan, Naxçivan, Nakhijevan, Nakhchawan, Nakhitchevan, Nakhjavan, and Nakhdjevan. Nakhchivan is mentioned in Ptolemy's Geography and by other classical writers as "Naxuana".

The older form of the name is Naxčawan (Armenian: Նախճաւան). According to philologist Heinrich Hübschmann, the name was originally borne by the namesake city (modern Nakhchivan) and later given to the region. Hübschmann believed the name to be composed of Naxič or Naxuč (probably a personal name) and awan, an Armenian word (ultimately of Iranian origin) meaning "place, town".

In the Armenian tradition, the name of the region and its namesake city is connected with the Biblical narrative of Noah's Ark and interpreted as meaning "place of the first descent" or "first resting place" (as if deriving from նախ, nax, 'first' and իջեւան, ijewan, 'abode, resting place') due to it being regarded as the site where Noah descended and settled after the landing of the Ark on nearby Mount Ararat. It was probably under the influence of this tradition that the name changed in Armenian from the older Naxčawan to Naxijewan. Although this is a folk etymology, William Whiston believed Nakhchivan/Nakhijevan to be the Apobatērion ("place of descent") mentioned by the first-century Jewish historian Flavius Josephus in connection with Noah's Ark, which would make the tradition connecting the name with the Biblical figure Noah very old, predating Armenia's conversion to Christianity in the early fourth century.