K Anbazhagan, DMK's General Secretary for 43 years, passed away in Chennai on Saturday at the age of 97.
He died at the Apollo Hospitals in Chennai after a prolonged illness.
Mr Anbazhagan was the General Secretary of DMK nine times from 1977. He was a nine-time MLA, one-time Lok Sabha member and former finance minister of Tamil Nadu and a close friend of former Chief Minister M Karunanidhi.
He was called Peraasiriyar (professor) as he worked as a lecturer at the Pachayappa college from 1944 to 1957. He later resigned and contested elections.
DMK President MK Stalin released a statement on Mr Anbazhagan's death on Saturday.
"DMK condoles the demise of General Secretary K Anbazhagan. DMK postpones all its party functions for 1 week and all DMK flags to fly half-mast for a week," the statement read.