Mongkut (18 October 1804 – 1 October 1868) was the fourth king of Siam from the Chakri dynasty, titled Rama IV. He reigned from 1851 until his death in 1868.
The reign of Mongkut was marked by significant modernization initiatives and diplomatic engagements, which played pivotal roles in shaping Siam's trajectory towards progress and international relations. It was during his reign that Siam first felt the pressure of Western expansionism. Mongkut embraced Western innovations and initiated reforms in technology, science, and culture, earning him the posthumous title "the Father of Science and Technology" in Siam. His accurate prediction of the total solar eclipse of 18 August 1868 — later dubbed "the King of Siam's eclipse" — demonstrated his scientific acumen and became a symbol of Siam's engagement with modern science.