Ust-Aldansky District (Russian: Усть-Алда́нский улу́с; Yakut: Уус-Алдан улууһа, Uus-Aldan uluuha, Yakut pronunciation: [uːs-aldan uluːha]) is an administrative[1] and municipal[5] district (raion, or ulus), one of the thirty-four in the Sakha Republic, Russia.

The area of the district is 18,300 square kilometers (7,100 sq mi).

[3] Its administrative center is the rural locality (a selo) of Borogontsy.

Its main rivers include the Lena and the Aldan.

[2] As of the 2021 Census, the ethnic composition was as follows:[10] The economy of the district is mostly based on agriculture.