Buddha Yodfa Chulaloke or Rama I the Great, was king of Thailand from 1782 to 1809.

He was born in Ayutthaya on March 20 1737 as son of Phra Aksorn Sundara Smiantra, a noble man in the Ayutthaya kingdom. He is believed to have Thai, Chinese, Persian, and even Greek in his family, but this is not proven. His birth name was Thong Duang. After getting education in a Buddhist temple, his father sent him to serve as a page for the later king Utumporn. There he met his friend Sin, the later king Taksin. After the fall of Ayutthaya he joined Taksin's army, and was known as Chao Phraya Chakri. The name Buddha Yodfa Chulaloke was given posthumously by king Nangklao (Rama III).

While Taksin's general, he conquered Vientiane in 1778/79, putting the country under vassalage, and removing its Emerald Buddha to Thonburi. In 1782, when Taksin was declared mad after a coup d'etat and was later executed, Yodfa assumed power, establishing the Chakri dynasty. He was crowned on April 6 as Rama I; the date is now a public holiday in Thailand.

King Rama I continued Taksin's task of saving the newly reunited country from attack by Burma, and repulsed several Burmese invasions. Culturally, Rama I also reestablished the traditions of the country by salvaging Buddhist texts lost in the chaos after the sacking of Ayutthaya by the Burmese in 1767. He also moved the capital from Taksin's capital of Thonburi and built the new capital Bangkok.In his palace, the Wat Phra Kaew, to house the Emerald Buddha, and created a new code of laws, the Book of three seals. As literature was his passion he also wrote a Thai version of the Ramayana epos called Ramakian.

He died on September 7 1809, and was succeeded by his son prince Isarasundorn, King Buddha Loetla Nabhalai (Rama II).