• King of Siam 1851 – 1868
• Chakri dynasty
• Buddhist monk 1824 – 1851

Outside Thailand, Mongkut is best known as the king in the 1951 musical and 1956 film The King and I, based on the 1946 film Anna and the King of Siam—in turn based on a 1944 novel by an American author about Anna Leonowens' years at his court, from 1862 to 1867, drawn from Leonowens’ memoir.

Mongkut was ordained as a Buddhist monk and remained in the monkhood for twenty-seven years before ascended the throne. During seventeen years of his reign, five new temples were built and about fifty temples were restored, the work being commissioned by King Mongkut.

Siam first felt the pressure of Western expansionism during Mongkut's reign. Mongkut embraced Western innovations and initiated the modernization of his country, both in technology and culture—earning him the nickname "The Father of Science and Technology" in Siam.

Mongkut was also known for appointing his younger brother, Prince Chutamani, as Second King, crowned in 1851 as King Pinklao. Mongkut assured the country that Pinklao should be respected with equal honor to himself (as King Naresuan had done with his brother Ekathotsarot in 1583). During Mongkut's reign, the power of the House of Bunnag reached its zenith: It became the most powerful noble family of Siam.