Ust-Yansky District is an administrative and municipal district, one of the thirty-four in the Sakha Republic, Russia. It is located in the north of the republic in the Yana River delta on the coast of the Laptev Sea and borders with Allaikhovsky and Abyysky Districts in the east, Momsky District in the south, Verkhoyansky District in the southwest, and with Bulunsky District in the west. The area of the district is 120,300 square kilometers (46,400 sq mi). Its administrative center is the urban locality of Deputatsky. Population: 6,810 (2021 Census); 8,056 (2010 Russian census); 10,009 (2002 Census); 41,265 (1989 Soviet census). The population of Deputatsky accounts for 37.0% of the district's total population.

Sakha, officially the Republic of Sakha (Yakutia), is the largest republic of Russia, located in the Russian Far East, along the Arctic Ocean, with a population of one million. Sakha comprises half of the area of its governing Far Eastern Federal District, and is the world's largest country subdivision, covering over 3,083,523 square kilometers (1,190,555 sq mi). Yakutsk, which is the world's coldest major city, is its capital and largest city.