The Thổ ethnic group inhabits the mountainous regions of northern Vietnam, mainly Nghệ An Province southwest of Hanoi. Many Thổ speak the Tho language, which is closely related to Vietnamese. The Thổ population numbered 91,430 in 2019.

Nghệ An is a coastal province near the northernmost part of the North Central Coast region, Central Vietnam. It borders Thanh Hóa to the north, Hà Tĩnh to the south, Xiangkhouang, Bolikhamsai and Houaphan of Laos to the west, and the East Sea to the east.