Phra Bat Somdet Phra Poramoruraja Maha Chakri Borommanat Phra Buddha Yodfa Chulaloke, posthumously titled "the Great", or Rama I (20 March 1736 – 7 September 1809), is the founder and the first monarch of the reigning House of Chakri of Siam (now Thailand).

He ascends the throne in 1782, after defeating a rebellion which had deposed King Taksin of Thonburi.

He is also celebrated as the founder of Rattanakosin (now Bangkok) as the new capital of the reunited kingdom.

Rama I was born in the Kingdom of Ayutthaya, and servei King Taksin in wars against the Burmese Konbaung dynasty and helps him in the reunification of Siam.

During this time, he emerges as Siam's most powerful military leader.

In 1782, he takes control of Siam and crowns himself as the monarch.

The most famous event in his reign is the Burmese-Siamese War of 1785, which is the last major Burmese assault on Siam.

Buddha Yodfa Chulaloke is also the first Somdet Chao Phraya, the highest rank the nobility can attain, equal to that of royalty.