The Sán Dìu (also known as San Deo, Trai, Trai Dat and Man Quan Coc; ; Chữ nôm: ; Vietnamese alphabet: Ngðá»Âi Sán Dìu) are an ethnic group in northern Vietnam who predominately speak Sán Dìu language, a Yue Chinese language. They are believed to have migrated from the Liangguang region of modern-day China around the 15th century.
The group's estimated population as of 2000 was 117,500; the 2019 census put the number at 183,004. They speak a variant of Yue Chinese, and it is suggested that some still speak Iu Mien. The major religions are Mahayana Buddhism and Taoism, with elements of animism and veneration of the dead. About 400 are adherents of the Catholic Church; a few are evangelical Protestants. This ethnic group is mainly concentrated around the Tam ÃÂảo range in Thái Nguyên Province.