Mountain Autonomous Soviet Socialist Republic or Mountain ASSR (Го́рская АССР Gorskaya ASSR) was a short-lived autonomous republic within the Russian SFSR in the Northern Caucasus that existed from January 20, 1921 to July 7, 1924.
Previously part of the Kuban and Terek Oblasts after the Russian Revolution a Mountainous Republic of the Northern Caucasus by the indigenous nationalities, however Soviet rule was installed after the Red Army conquered the Northern Caucasus in the course of the Russian Civil War, and the former republic was transformed into the a Soviet one. The area was over , and the population was about 800,000. It comprised six national districts: Karachay, Kabardin, Balkar, Ossetian, Ingush and Chechen, and two cities: Grozny and Vladikavkaz. In addition a special province level autonomy was provided to Terek Cossacks the Sunzha Cossack District, which included a large enclave in northern Ingushetia, and a smaller one bordering Grozny.
Partition of the GASSR began shortly after it was formed when the Kabardian National district was separated into the Kabardin Autonomous Oblast and directly subjected to the RSFSR on 1 September, 1921. Next came the Karachay district from which the Karachay-Cherkess Autonomous Oblast was created on 12 January, 1922, the Balkar District followed on 16 January 1922, and merged with the Kabardin A.O to form the Kabardino-Balkar Autonomous Oblast. The Chechen district was separated on 30 November, 1922 into the Chechen Autonomous Oblast.
By the July 7,1924 decree of the VTsIK the GASSR was partitioned into the North Ossetian Autonomous Oblast and the Ingush Autonomous Oblast. The Sunzha Cossack District and the city of Vladikavkaz were directly subordinated to the VTsIK until 17 October 1924 when the North-Caucasus Krai was formed and integrated all of the former GASSR in addition to those two units.