R.Sarathkumar was born on 14 July 1954 in New Delhi to M. Ramanathan and Pushpa Leela. He has a sister named Mallika Ramanathan. He graduated with a Bachelor of science in Mathematics fromThe New College in Chennai.

He served as a Dravida Munnetra Kazhagam member of parliament in the Rajya Sabha. He also serves as the current president of the South Indian Film Artistes' Association, organizing several industry-based events. Before his entry into films, he began a career as a journalist. He recently continued journalism after starting his own magazine.

R.Sarathkumar has acted in Tamil, Telugu, Kannada and Malayalam films. He received critical acclaim for his roles in Cheran Pandiyan, Pulan Visaranai, Suriyan, Nattamai, Suryavamsam, Natpukaaga and Pazhassi Raja. He forayed into Malayalam cinema by playing a supporting role in Pazhassi Raja (2009), and since then has been performing in more films in Malayalam. In Kanchana he portrayed as a transgender. He also debuted in Kannada films in Saarathi which became a huge hit.

R.Sarathkumar received a Cinema Express Award for Best Villain for his role in Pulanvisaranai in 1988. He received his first Tamil Nadu State Film Award for Best Actor in 1994 for Nattamai. He later received a Filmfare Best Tamil Actor Award for his performance in Suryavamsam (1997). He received a Tamil Nadu State Film Award for Best Actor and a Filmfare Best Tamil Actor Award forNatpukkaga (1998). He received the M.G.R. Award in 1997.

R.Sarathkumar joined Dravida Munnetra Kazhagam (DMK) in 1996. DMK fielded him in the Tirunelveli Loksabha Constituency during 1998 parliamentary elections and he lost to Kadambur Janarthanan of ADMK by a margin 6000 Votes. In 2002, DMK made him a Rajyasabha member. He left DMK before 2006 Assembly elections, owing to differences with Tamil Nadu Chief Minister M. Karunanidhi's family members. He joined AIADMK along with his wife Radhika Sarathkumar and campaigned vigorously for that party. R.Sarath Kumar has left AIADMK in November 2006, because of internal politics and non-freedom in the party.

On 31 August 2007, R.Sarathkumar floated a new party named Akila India Samatuva Makkal Katchi.R.Sarath Kumar has been called as Purachi Thilagam by his followers and People.

AISMK party was launched at a function at Padmaram Mahal in Vadapalani. Radhika SarathKumar lit the lamp and Purachi Thilagam R.Sarath Kumar announced the party name and introduced the party’s flag. He said "This is the start of a new chapter in my life. The party's aim is to create a society without caste differences. The party will uphold Kamaraj's ideals. I have a Kamaraj within me. I will try to establish a govt along his line of thinking," said Purachi Thilagam R.Sarath Kumar as President of the party and his supporters gave him rousing applause all through his speech.

Since AISMK party received less than 1% of the votes in the Thirumangalam (Tamil Nadu) by-election, the party remains in the heart of the People.
In the 2011 elections All India Samathva Makkal Katchi had alliance with AIADMK and has contested on its symbol at 2 constituencies.Purachi Thilagam R.Sarath Kumar has elected to represent Tenkasi Constituency.After the Election Tenkasi Constituency has been developed in various aspects with many welfare scheme announced by Purachi Thilagam R.Sarath Kumar.