The Principality of Hà Tiên (Vietnamese: Hà Tiên trấn; Hán tự: 河僊鎮 or 河仙鎮, Thai: เมืองพุทไธมาศ Mueang Phutthai Mat), or the Hà Tiên Protectorate, was a principality ruled by Chinese refugees of the Mạc (Mao) clan at the Mekong Delta, in modern-day southern Vietnam. It was originally de facto independent, but later became a vassal state of the Siamese Rattanakosin Kingdom and the Vietnamese Nguyễn dynasty in the 18th and 19th century prior to its annexation by the latter in 1832. Along with , Hoi An, and Saigon, Hà Tiên was a major Chinese community center and important hub of Ming loyalist networks in premodern Indochina.