S. R. Nathan born in Singapore, he graduated from the University of Malaya in 1954, with a diploma in social studies. He became a medical social worker in the Singapore Civil Service in 1955 before joining the Ministry of Foreign Affairs in 1966. He also worked for the ministries of Home Affairs (1971) and Defence (1971-1979), before returning to the Foreign Ministry.
From 1982 he became executive chairman of The Straits Press, a Singapore newspaper company, and was involved with several other companies on a directorial level. He also served on a number of social and cultural government committees, including five years as chairman of the Hindu Endowments Board, and was a founding member of the Singapore Indian Development Agency. He served as high commissioner to Malaysia in 1988, and then as ambassador to the United States from 1990 to 1996. As the only candidate to receive a certificate of eligibility from the government, Ramanathan was elected president in the election of 1999, succeeding Ong Teng Cheong.