Usun (; , Uhun) is a rural locality (a selo), the only inhabited locality, and the administrative center of Kyuletsky 1-y Rural Okrug () in Vilyuysky District of the Sakha Republic, Russia, located from Vilyuysk, the administrative center of the district. Its population as of the 2010 Census was 801, up from 743 recorded during the 2002 Census.
It has a high school, agricultural enterprise, kindergarten, shop, communication center, district hospital, and bank.