Ust-Yansky Ulus (Russian: Усть-Янский улус) is an ulus (district) of the Sakha Republic in Russia. It is located in the northern part of the republic, at the Yana River delta on the coast of Laptev Sea. The ulus is bordered by Allaikhovsky and Abyysky uluses in the east, Momsky Ulus in the south, Verkhoyansky Ulus in the southwest, and Bulunsky Ulus in the west.
The area of Ust-Yansky Ulus is 120,300 km². Its administrative center is the settlement of Deputatsky. The ulus is administratively divided into three settlements and seven naslegs. The main industries are gold mining, reindeer herding, fishing, and fur trade.