Phra Bat Somdet Phra Poramenthramaha Mongkut Phra Chom Klao Chao Yu Hua; or Rama IV; known in foreign countries as King Mongkut (18 October 1804 - 1 October 1868); was the fourth monarch of Siam (Thailand) under the House of Chakri; ruling from 1851-1868. He was one of the most revered monarchs of the country.

Outside of Thailand; he is best-known as the King in the 1951 play and 1956 film The King and I; based on the 1946 film Anna and the King of Siam - in turn based on the 1944 novel about Anna Leonowens' years at his court; from 1862 to 1867.