Pierre Martin Ngô Đình Thục was the Roman Catholic Archbishop of Huế, Vietnam, and later a sedevacantist bishop who was excommunicated by the Catholic Church and later reconciled with the church before his death in 1984. He was a member of the Ngô family who ruled South Vietnam in the years leading up to the Vietnam War. He was the founder of the Dalat University. Today, thousands of men from various Independent Catholic, sedevacantist, and neo-Gnostic groups claim to have derived their apostolic succession from Thục.
While Thục was in Rome attending the second session of the Second Vatican Council, the 1963 South Vietnamese coup overthrew and assassinated his younger brother, Ngô Đình Diệm, who was president of South Vietnam. Thục was unable to return to Vietnam and lived the rest of his life exiled in Italy, France, and the United States. During his exile, he was involved with Traditionalist Catholic movements and consecrated a number of bishops without the Vatican's approval for the Palmarian and Sedevacantist movements. As a result, he was excommunicated by the Holy See and later reconciled with the Vatican.