Ust-Maysky District (; , Uus-Maaya uluuha, ) is an administrative and municipal district (raion, or ulus), one of the thirty-four in the Sakha Republic, Russia. It is located in the east of the republic and borders with Oymyakonsky District in the northeast, Okhotsky District and Ayano-Maysky District of Khabarovsk Krai in the east and south, Aldansky District in the southwest, Amginsky District in the west, Churapchinsky and Tattinsky Districts in the northwest, and with Tomponsky District in the north. The area of the district is . Its administrative center is the urban locality (a settlement) of Ust-Maya. Population: 11,568 (2002 Census); The population of Ust-Maya accounts for 33.9% of the district's total population.
The main rivers in the district are the Aldan and its tributaries the Maya and Allakh-Yun.
Average January temperature ranges from and average July temperature ranges from in the mountains to in the river valleys. Annual precipitation ranges from .
The district was established on May 20, 1931. The administrative centre of the district was Solnechny from 1972 to 1992, after which it moved to Ust-Maya.
As of the 2021 Census, the ethnic composition was as follows:
The economy of the district is mostly based on mining, timber industry, and production of construction materials. There are deposits of gold, lead, zinc, rare metals, and construction materials.
<small>Divisional source:</small><br /> <br/> <small>*Administrative centers are shown in bold</small>