Nuosu or Nosu, also known as Northern Yi, Liangshan Yi, and Sichuan Yi, is the prestige language of the Yi people; it has been chosen by the Chinese government as the standard Yi language and, as such, is the only one taught in schools, both in its oral and written forms. It was spoken by two million people and was increasing ; 60% were monolingual. Nuosu is the native Nuosu name for their own language and is not used in Mandarin Chinese, though it may sometimes be translated as Nuòsūyǔ.

The Yi or Nuosu people are an ethnic group in southern China. Numbering nine million people, they are the seventh largest of the 55 ethnic minority groups recognized by the Chinese government. They live primarily in rural areas of Sichuan, Yunnan, Guizhou, and Guangxi, usually in mountainous regions. The Liangshan Yi Autonomous Prefecture is home to the largest population of Yi people within China, with two million Yi people in the region. In neighbouring Vietnam, as of 2019, there are 4,827 Lô Lô people living in the Hà Giang, Cao Bằng, and Lào Cai provinces, in the country's north.