Ratsadathirat is the twelfth king of Ayutthaya, an ancient kingdom in Thailand.

He is a son of Borommarachathirat IV and succeeds his father to the throne of Ayutthaya at the age of five in 1533–34 CE).

The following year, after having been on the throne for five months, he is put to death by his relative, Chairachathirat, who then assumed the kingship.