fiercely independent tribal chief of Tai peoples in the Black River region of Tonkin (now northern Vietnam) who created a semiautonomous feudal kingdom and coexisted with the French, who ruled the rest of Vietnam.

Deo Van Tri was the son of Deo Van Seng, chief of the Tais who occupied the Vietnamese lands surrounding the Black River. As the head of a band of Chinese pirates, Deo Van Seng had seized the area in 1869. Deo Van Tri at age 16 joined with his father to repel a Shan invasion, and, together with the Black Flag pirate bands, he defended the kingdom of Vietnam. For his bravery the Vietnamese court named Deo Van Tri chief and accorded his father a mandarin title. When rival pirate bands threatened his father's principality of Muong Theng, Deo forced their retreat into China's Yunnan province.

In 1885, with Tonkin at war against France, Deo again served the Vietnamese loyally. He offered refuge to the young rebel king, Ham Nghi, and the regent, Ton That Thuyet. The regent, however, tried to assassinate Deo in order to ensure the secrecy of their whereabouts. Deo thenceforth refused to associate with the Vietnamese resistance effort.

Deo, encouraged by his family, came to terms with France in 1888 to protect his people's independence, agreeing to serve the French colonial regime. He accompanied the French explorer Auguste Pavie (Pavie, Auguste) on several journeys and on a mission to China, and he permitted members of his family to travel with Pavie to Paris, where they were enrolled at schools. Continuing this policy of cooperation, Deo assisted in operations delimiting the Indochinese frontier with China in 1894.