Ust-Udinsky District is an administrative district, one of the thirty-three in Irkutsk Oblast, Russia. Municipally, it is incorporated as Ust-Udinsky Municipal District. The area of the district is 20,400 square kilometers (7,900 sq mi). Its administrative center is the urban locality of Ust-Uda. Population: 14,385 (2010 census); 16,747 ; 28,790 (1989 Soviet census). The population of Ust-Uda accounts for 36.0% of the district's total population.