Trình Minh Thế (1920 – May 3, 1955) was a Vietnamese nationalist and military leader during the end of the First Indochina War and the beginning of the Vietnam War.
Thế was born in Tây Ninh Province and raised in the Cao Đài religion. He was trained in military officer school by the Japanese Kempeitai when Japan began using Cao Đài paramilitary troops. By 1945, he was an officer in the Cao Đài militia.
In June 1951, Thế broke from the Cao Đài hierarchy and took about 2,000 troops with him to form his own militia, the Liên Minh, devoted to combating both the French and the Việt Minh. Thế's father and one of his brothers formed their own military group in the Liên Minh and were later killed in combat by Việt Minh.
Thế's forces were implicated in a series of terrorist bombings in Saigon from 1951 to 1953—which were blamed on communists at the time—and may also have been responsible for the assassination of the French General Chanson at Sa Đéc in 1951.
In 1954, United States military advisor Edward Lansdale negotiated with Thế to use his militia to back up Ngô Đình Diệm and the ARVN. On February 13, 1955, Thế's troops were officially integrated into the South Vietnamese army, where he assumed the rank of general. He led the Liên Minh on a triumphal march into Saigon.
Through Lansdale, the U.S. continued to fund Thế and other Caodaist groups. However, as the South Vietnamese government faltered, many of the militia leaders declared their open opposition to Diệm and began an attempted coup. Thế's loyalties at this point were unclear, and it was also unclear whether the U.S. intended to support Diệm against the rebels; some said that Thế might be a realistic replacement for Diệm. However, when the Liên Minh entered Saigon again it appeared to be in response to Lansdale's last-minute call for them to protect Diệm.