The Tajik Autonomous Soviet Socialist Republic (Tajik ASSR) was an autonomous republic within the Uzbek SSR in the Soviet Union. It was created in October 1924 by a series of legal acts that partitioned the three existing regional entities in Central Asia – Turkestan ASSR, Bukharan People's Soviet Republic, and Khorezm People's Soviet Republic – into five new entities based on ethnic principles: Uzbek SSR, Turkmen SSR, Tajik ASSR (within Uzbek SSR), Kyrgyz Autonomous Oblast (as a province of RSFSR), and Karakalpak Autonomous Oblast (as a province of Kazakh ASSR).
The capital of Tajik ASSR was in Dyushambe (today's Dushanbe). In October 1929, Tajik ASSR was transformed into a full-fledged Soviet Socialist Republic and became Tajik SSR, which additionally absorbed the Khojent region (today's Sughd Province in northern Tajikistan) from Uzbek SSR. Tajik SSR existed until the creation of the independent Republic of Tajikistan in September 1991.