Thawisan Ladawan (Thai: ???????? ????????; 26 January 1923 – 7 April 2006) was husband of Busba Kitiyakara (younger sister of Queen Sirikit), a member of King Bhumibol Adulyadej's Privy Council, and for 26 years, principal private secretary to the King.
Thawisan attended Vajiravudh College and graduated from the inaugural class of Faculty of Law, Thammasat University in 1938.
After graduated, he worked in the Ministry of Foreign Affairs.
He worked in several capitals, including Paris and Brussels, and earned a Diplome d'Etudes Superieures de Droit International Public from Paris University in 1954.
He became Deputy Director-General of the Protocol Department before departing in 1968 to serve as Deputy Principal Private Secretary to King Bhumibol.
A year later he became King Bhumibol's Principal Private Secretary, and was later appointed to the Privy Council.
He died at the age of 83 due to chronic liver disease.