The Treaty of Alexandropol (Armenian: Ալեքսանդրապոլի պայմանագիր; Turkish: Gümrü Anlaşması or "Gyumri Treaty") was a peace treaty between the First Republic of Armenia and the Grand National Assembly of Turkey. The treaty formally ended Turkey's invasion of Armenia that had begun on 12 September 1920.

It was signed by the Armenian Foreign Minister Alexander Khatisyan in the early hours of 3 December 1920; however, the previous day, the Armenian government in Yerevan had resigned and transferred power to a Soviet government and so Khatisyan was no longer acting on behalf of the government of Armenia, and the treaty was invalid.

The terms of the Alexandropol Treaty were prepared by Turkey, with no concessions made to the Armenians. Turkey rejected Khatisyan's appeals for the inclusion of Surmalu, Mount Ararat, and the medieval capital of Ani, for their significant importance to Armenian culture and history.

The Alexandropol Treaty forced Armenia to forfeit all claims to Western Armenia which had been promised under the Treaty of Sevres, reduce its military to a token force, and accept Turkish oversight. Turkey was to assume control over transportation and communications, thereby reducing Armenia to a Turkish protectorate or vassal state. Turkey was granted the right of transit through Armenian territory. A large part of the south of Yerevan province was ceded to Azerbaijan, later to become the Turkish protectorate of Nakhchivan.

The Alexandropol Treaty also changed the boundary of the First Republic of Armenia to the Ardahan-Kars borderline and ceded over half of First Republic of Armenia to the Grand National Assembly of Turkey. The tenth item in the agreement required that Armenia renounce the Treaty of Sèvres.

The new borders were ratified by the Treaty of Kars, signed by the Grand National Assembly of Turkey and, at Soviet Russia's insistence, the three Soviet republics of Armenia, Georgia, and Azerbaijan.^{[citation needed]}

An abbreviated version of the treaty terms is as follows: