达信大帝（泰语：สมเด็จพระเจ้าตากสินมหาราช，皇家转写：Somdet Phra Chao Taksin Maharat  发音；1734年4月17日－1782年4月7日），即波隆罗阇四世（สมเด็จพระบรมราชาที่ 4），是泰国吞武里王朝创建者和唯一一位君主，1767年至1782年在位。

原名信（สิน），又名郑信、郑新、郑国英，是中泰混血儿，其父姓郑，具有潮州民系的血统。他在《清史稿》中以郑昭之名登场。

郑信原为大城王朝的一名将领。缅甸贡榜王朝吞并暹罗之后，郑信起兵反抗缅甸的统治，最终驱逐了缅甸侵略者，平定各地割据势力，于1769年创建吞武里王朝。在位期间，击退了缅甸的再次入侵，征服了兰纳、万象、瑯勃拉邦、占巴塞，威胁真腊（今柬埔寨）。此外，还致力于推进泰国的教育和宗教学习，并积极同中国、英国与荷兰展开贸易活动。晚年受到精神疾病的困扰，引起官员的不满。1782年，在一次宫廷政变中被废黜。将军昭披耶却克里自真腊归国，平定叛乱并处决了郑信，自称国王，创建曼谷王朝。

Taksin the Great (Thai:สมเด็จพระเจ้าตากสินมหาราช, rtgs: Somdet Phra Chao Taksin Maha Rat,  listen ) or the King of Thonburi (Thai:สมเด็จพระเจ้ากรุงธนบุรี, rtgs: Somdet Phra Chao Krung Thon Buri; Chinese:郑信; pinyin:Zhèng Xin; Teochew: Dên Chao; Vietnamese: Trịnh Quốc Anh) (April 17, 1734 – April 7, 1782) was the only King of the Thonburi Kingdom and was of Thai Chinese heritage. He was a leader in the liberation of Siam from Burmese occupation after the Second Fall of Ayutthaya in 1767, and the subsequent unification of Siam after it fell under various warlords. He established the city Thonburi as the new capital, as the city Ayutthaya had been almost completely destroyed by the invaders. His reign was characterized by numerous wars, fought to repel new Burmese invasions and to subjugate the northern Thai kingdom of Lanna, the Laotian principalities, and a threatening Cambodia. He was executed and succeeded by his long-time friend Maha Ksatriyaseuk who then assumed the throne, founding the Rattanakosin Kingdom and the Chakri dynasty, which rules Thailand to this day.