Thawisan Ladawan (Thai: ทวีสันต์ ลดาวัลย์; 26 January 1924 – 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 King Bhumibol Adulyadej.

Thawisan attended Vajiravudh College and graduated from the inaugural class of Faculty of Law, Thammasat University in 1938.

After graduating, he worked in the Ministry of Foreign Affairs in several capitals, including Paris and Brussels, and earned a Diplome d'Etudes Superieures de Droit International Public from Paris University in 1954.

A year later he became Bhumibol's Principal Private Secretary, and was later appointed to the Privy Council.

Thawisan was the son of Phra Phum Phichai (Mom Ratchawong Bung Ladawan) and Nueang Bunnag.