The former subject of the Russian Federation, one of the 6 districts, liquidated as a result of the enlargement of the regions in 2003-2008. It was located in the northeastern part of Russia on the territory of the Irkutsk Oblast. It had no borders with other subjects of the Russian Federation. Ust-Orda Buryat AD was a subordinate entity of the Russian Federation and at the same time was a member of another entity (Irkutsk Oblast). In 2006, a referendum was held to merge the Irkutsk Oblast and the Ust-Orda Buryat Autonomous Okrug, which resulted in the creation of a new constituent entity of the Russian Federation in 2008. The Ust-Orda Buryat Autonomous Okrug entered this entity as an administrative and territorial unit with a special status.
The district was formed in September 1937 as the Ust-Orda Buryat-Mongolian national Okrug in the Irkutsk Oblast. In 1958, it was renamed the Ust-Orda Buryat National Okrug, and in 1978 it was reorganized into the Ust-Orda Buryat Autonomous Okrug. In 1990, a declaration was adopted, and the district was declared a subordinate entity of the Russian Federation, as a part of the Irkutsk Oblast.
The titular ethnic group in the district were Buryats. According to the 2002 census, they made up 39.6% of the population of the district, while Russians - 54.4%. The Buryats differ from the titular nation of the country in language and religion. The Buryat language belongs to the Central Mongolic group of Mongolic languages. Since the end of the XVI century, the Tibetan Buddhism of the Gelugpa school has been widely spread among the Buryats. There are also traditional beliefs, which are termed Shamanism or Tengrism.