The First Republic of Armenia, officially known at the time of its existence as the Republic of Armenia, was the first modern Armenian state since the loss of Armenian statehood in the Middle Ages.

The republic was established in the Armenian-populated territories of the disintegrated Russian Empire, known as Eastern Armenia or Russian Armenia. The leaders of the government came mostly from the Armenian Revolutionary Federation (ARF or Dashnaktsutyun). The First Republic of Armenia bordered the Democratic Republic of Georgia to the north, the Ottoman Empire to the west, Persia to the south, and the Azerbaijan Democratic Republic to the east. It had a total land area of roughly 70,000 km2, and a population of 1.3 million.

The Armenian National Council declared the independence of Armenia on 28 May 1918. From its very onset, Armenia was plagued with a variety of domestic and foreign issues. A humanitarian crisis emerged from the aftermath of the Armenian genocide as hundreds of thousands of Armenian refugees from the Ottoman Empire were forced to settle in the fledgling republic. Lasting two and a half years in existence, the Republic of Armenia became involved in several armed conflicts with its neighbors, caused by overlapping territorial claims. By late 1920, the nation was partitioned between the Turkish Nationalist forces and Russian Red Army. The First Republic, along with the Republic of Mountainous Armenia which repelled the Soviet invasion until July 1921, ceased to exist as an independent state, superseded by the Armenian Soviet Socialist Republic that became part of the Soviet Union in 1922.