Si Suthammaracha (Thai: ศรีสุธรรมราชา, Śrī Sudharmarājā) was the King of Ayutthaya from August 1656 to 26 October 1656 (2 months 17 Days).

Not long after Si Suthammaracha seized the throne from Chao Fa Chai, He quarrelled with his nephew, Prince Narai, They began to fight against each other, Si Suthammaracha was captured and executed after defeated in single combat with Narai on 26 October 1656.

Si Suthammaracha’s rule was weak and he fell under the control of Chao Phraya Chakri, an ambitious mandarin who also wanted the throne.

He drew his support from the Persian, and Japanese mercenaries that had been persecuted during his father's reign as well as the Dutch.

The prince engaged in single combat with his uncle, until the king fled to the Rear Palace.