The Iu Mien are the largest of the groups who form the official Yao nationality in China. This group calls themselves Iu Mien or simply Mien, but in China they are widely known by their Chinese name Pan Yao. Little was known about this isolated group until recent years. In 1937 one traveler commented, "In these lofty areas are the aboriginal tribes called the Iu people, the 'Red Indians' of China. They are yet to be studied in detail."

The Iu Mien language is remarkably uniform considering the wide dispersion of its speakers. In 1987, Iu Mien able to speak their language numbered 692,000. The remainder now speak Chinese.

The Iu Mien have a long history of fleeing oppression. This explains why the Chinese sometimes call them the Guoshan (Crossing the Mountains) Yao. Linguist Herbert Purnell explains, "The Iu Mien have been profoundly influenced by the Chinese over many centuries of contact. Perhaps the most significant development from these contacts has been the evolution and preservation of Taoist rituals written in Chinese characters. The Iu Mien have therefore possessed for several centuries what many other Asian peoples only dream of - an extensive written literature."

The Han Chinese call the Iu Mien Pan Yao after their legendary ancestor and pioneer of the Yao race, Pan Hu. Pan can be traced in historical Chinese records as far back as the fifth century AD. The Chronicles of the Later Han Dynasty ("Hou Han Shu") "tells the story of Pan Hu, the pet dog of Emperor Gao Xin (2435-2365 BC) who killed his lord's arch-enemy, General Wu, the chief of the Quan Rong tribe. The dog was rewarded by marrying a young princess." Their descendants, known as "the race of Pan Hu," became the forefathers of the Iu Mien. At some time the Imperial Court issued The King Ping's Charter. This proclamation was designed to reward the Yao by perpetually releasing them from paying taxes.

The Iu Mien are Daoists who also worship their ancestors. They believe Pan created the heavens and the earth. "After the death of King Pan the feudal court allowed his descendants to worship and make a picture of him with human features."

Although one source estimates 10,000 Iu Mien/Yao Christians in China, the true number is probably much lower. In recent years, at least 1,000 "Red Head" Yao (an Iu Mien group) living in Jinping County, Yunnan Province, have come to Christ because of FEBC gospel radio broadcasts in their language.