The government has included the Lesu as part of the Yi nationality in China, an artificially constructed classification that contains at least "several dozen branches" of different ethnic groups. Lesu or Leisu is the self name of this group. The Chinese call them Shansu, meaning "mountain people." The Lesu who live west of the Gasa River in the Ailao Mountains of Mosha District reportedly no longer speak their mother tongue, having reverted to Chinese. Because of this, the people in the area call them Jia Shansu, meaning "fake Shansu."
The Lesu were once named the Ma Long people, who were part of the Sou tribe dating back to the Han and Western Jin dynasties (220 BC - AD 316). "The Lesu entered Yuanjiang County during the Yuan Dynasty (1271-1368) and by the Ming Dynasty (1368-1644) had spread to Xinping and Shiping counties."
There are two different sets of festivals celebrated by the Lesu of different areas. Those in Eshan, Xinping, and Shuangbai celebrate a festival called Traditional Flower Fair, while those in Yuanjiang celebrate a Mountain Sacrifice Festival. The Flower Fair of the first region is celebrated every 24th day of the sixth lunar month (the same day as the Torch Festival among the Nisu and Nasu), and repeated every 15th day of the seventh month of the Lunar calendar. The festival stems from an old legend in which a Han and a Lesu fell in love. Their parents strongly disagreed with the engagement, however. One night the couple went to the peak of Daxishan where they danced and sung. On that night the two committed suicide together. The festival is now held in their honor.
The Lesu people greatly revere the Mountain god, but only those in Yuanjiang County hold a yearly day of sacrifice in order to appease him. On this day Lesu are forbidden to work in their fields for fear the Mountain god will be offended.
The Lesu were a completely unevangelized and unreached people group until 1999, when a Lesu family - who helped record the first gospel recording in their language - gave their lives to Jesus Christ after considering the message.