Mukhsha Ulus (Tatar: Мухша олысы, Muxşa olısı, موحشا ﯘلىسى), or Naruchat Duchy (Tatar: Наручат бәклегел, Naruçat bäklege) was a subdivision of Golden Horde at the place of modern Mordovia, Penza Oblast and Tambov Oblast of Russia in 13th-15th centuries with the capital in Mukhsha. The main territory of the ulus (district) was situated between rivers Sura and Tsna. The previous population were Mordvins and Burtas. Population was mainly Mişär Tatars, and Moksha Mordvins. In 1313-1367 years coined own money. Population was mostly agricultural. Some were cattle-breeders and craftsmen. In 1360 Tağay beg conquered the ulus. It became a semi-independent duchy. In 1367 Mamai conquered that duchy. In the end of 14th century duchy declined and in the beginning of 15th century Russians conquered it.
Naruçat Duchy was a place where Mişär Tatars and Mişär dialect were formed.