emperor of Vietnam who followed a policy of conservatism and isolation and whose persecution of Christian missionaries foreshadowed the French conquest of Vietnam.

The son of Emperor Thieu Tri, Prince Nguyen Phuoc Hoang Nham was chosen over his older brother to succeed his father. He ascended the throne in 1847, taking the reigning name Tu Duc. He continued his father's persecution of missionaries and opposition to trading and diplomatic relations with European powers. Executions reached such proportions that the French in 1856 sent a formal letter of protest to the court of Hue.

The decapitation of the Spanish bishop José María Díaz in 1857 brought immediate reprisals: French forces occupied Tourane (Da Nang) in 1858 and defeated the Vietnamese at several key centres in southern Vietnam. As a result, Tu Duc was forced in 1862 to cede to France his three southern provinces in a treaty that subsequently became a source of dispute. The French referred to this area as Cochinchina.

Tu Duc's reign was further disrupted by rebellions in 1865, led by a pretender to the throne from the rival Le dynasty. A French attack on the citadel of Hanoi in 1873 resulted in the granting of trade concessions to France and the opening of the Red River in the north to European commercial shipping. Tu Duc appealed to China for protection, pleading the cause of Vietnam as one of China's vassal states, but the French deployed more forces and gradually secured more territory. Within four years of Tu Duc's death, the French established the Indochinese Union.