The Republic of Aras (Azerbaijani: Araz Respublikası; also known as the Republic of Araks or the Araxi Republic) was a short-lived and unrecognized state in the South Caucasus, roughly corresponding with the territory that is now the Nakhchivan Autonomous Republic of Azerbaijan. Named after the Aras River that formed its southern border, the republic was declared in December 1918 by Jafar Kuli Khan Nakhchivanski with support from the Azerbaijan Democratic Republic's ruling party, the Musavat Party, and the Young Turk government of the Ottoman Empire.
The creation of the Republic of Aras was in response to a border proposal by Sir John Oliver Wardrop, British Chief Commissioner in the South Caucasus, that would have assigned the area to the Armenian Republic. Its existence was ended when troops from the Democratic Republic of Armenia advanced into the region and succeeded in taking control over it in mid-June 1919 during the Aras War. However, this triggered an advance into the Nakhichevan region by the army of the Azerbaijan republic, and by the end of July Armenia had lost control of the region.