Along with Singapore Minister Mentor Lee Kuan Yew, now 82, Rajaratnam was a founding member of the dominant People's Action Party that has controlled the government since the former British colony's first full general elections in 1959.
Sri Lankan-born Rajaratnam served 29 years in the island republic's cabinet, including stints as foreign minister and deputy prime minister, retiring from politics in 1988.
''We mourn S Rajaratnam's death as we remember his profound contribution to the nation. Singapore has lost a giant,'' Singapore's Foreign Affairs Ministry said in a statement.
The statement did not give the cause of death but local media said Rajaratnam died of heart failure.
Rajaratnam, a former journalist, was also seen as a driving force behind the formation of the Association of Southeast Asian Nations regional grouping.
REUTERS SHR RK1829