Sarathkumar Ramanathan is an Indian film actor, producer, and politician who has made a significant impact on the South Indian film industry.

Ramanathan studied at the Raja Muthiah High School in Chennai. Later, he went to the Central School in IIT Madras and completed his further studies at St. Patrick's Anglo Indian Higher Secondary School.

He was quite interested in sports; he played cricket, football, and hockey, even representing his school and college in numerous tournaments. He also joined the NCC and became an Air Wing Cadet. Ramanathan completed his pre-university education at Loyola College. He then pursued a Bachelor of Science in Mathematics from The New College in Chennai.

In 1974, Ramanathan became a bodybuilder and earned the title of Mr Madras University. Later, he moved to Bangalore to work for Dinakaran, a Tamil newspaper. While he started off as a newspaper distributor, he went on to become a reporter for Dinakaran. He then shifted back to Chennai and opened a travel agency, where he met Kannadasan, who encouraged him to become a film producer.

Ramanathan then transitioned to acting and made his debut in the film industry in 1986 with the Telugu film Samajamlo sthree (1986). He was supposed to play the lead role in Chinna Poove Mella Pesu (1987) but was replaced by Prabhu. In 1988, he produced and acted in the Tamil film Kan Simmittum Neram (1988). One of his first major roles was in the movie Pulan Visaaranai (1990), where he played the role of a villain.

Soon after, he started getting more offers, which led to him acting in films like Mr. Karthik (1990), Pudhu Padagan (1990), Velai Kidaichiruchu (1990), Raja Kaiye Vacha (1990) and Urudhi Mozhi (1990). He also worked in several Telugu films, including Magaadu (1990) and Balachandrudu (1990). Following this, he essayed supporting roles in many Tamil films, such as Salem Vishnu (1990), Sirayil Sila Raagangal (1990), and Mounam Sammadham (1990).

In 1991, he featured in twelve Tamil films and three Telugu movies, mostly in supporting roles. The same year, he appeared in lead roles in films like Kaaval Nilayam (1991) and Cheran Pandian (1991), which were quite successful commercially.

His major breakthrough role came in the 1992 film Surieyan (1992), considered a trendsetter for Tamil action films. In addition to positive reviews, this role got him the Cinema Express Best Actor Special Award. He also worked on other films in 1992, including Thai Mozhi (1992), Ellaichami (1992), Samundi (1992), and Natchathira Nayagan (1992).

In 1993, Ramanathan acted in films like Aadhityan (1993), Dasarathan, Vedan (1993), Band Master (1993), and Moondravathu Kann (1993). In 1994, some of his projects included Aranmanai Kaavalan (1994), Captain Shiva (1994), Raja Pandi (1994), and the critically-acclaimed Nattamai (1994), for which he won the Best Actor award at the Tamil Nadu State Film Awards, Filmfare Awards, and Cinema Express Awards.

Ramanathan continued to be incredibly prolific; he featured in various films over the years, like Veluchami (1995), Coolie (1995), Ragasiya Police (1995), Mahaprabhu (1996), Nethaji (1996), Aravindhan (1997), Suryavamsam (1997), Janakiraman (1997), Moovendhar (1998), Natpukkaga (1998), Chinna Durai (1999), Maayi (2000), Rishi (2001), Vinnukum Mannukum (2001), Samudhram (2001), Thenkasi Pattanam (2002), Paarai (2003), Chatrapathy (2004), Aai (2004), etc.

In 2005, he acted in Ayya (2005), which was successful and received positive reviews. He also appeared in guest roles in Bunny (2005) and Jithan (2005). In 2006, he directed and acted in Thalaimagan (2006), which was a commercial failure. He appeared in several other films, including Pachaikili Muthucharam (2007), Nam Naadu (2007), and Vaitheeswaran (2008), which received mixed to negative reviews.

In 2009, Ramanathan debuted in Malayalam cinema through Kerala Varma Pazhassi Raja (2009). He won the Vanitha Film Award for Best Supporting Actor for his role. He also appeared in Jaggubhai (2010), Kola Kolaya Mundhirika (2009), Oridathoru Postman (2010), The Metro (2011), and Christian Brothers (2011).

In 2011, he played a transgender person in Kanchana: Muni 2 (2011), which was a commercial success. He appeared in Achante Aanmakkal (2012) and Myna (2013). In 2014, he appeared in Nimirndhu Nil (2014), Janda Pai Kapiraju (2015), and Kochadaiiyaan (2014). In 2017, he made a comeback in Tamil cinema with Chennaiyil Oru Naal 2 (2017).

Besides his career in the entertainment industry, Ramanathan has been actively involved in politics. He joined the Dravida Munnetra Kazhagam (DMK) party in 1996 and launched the All India Samathuya Makkal Kathci (AISMK) party in 2007. He is also a former Member of the Legislative Assembly of the Tenkasi Constituency and served for three terms as the president of the Nadigar Sangam from 2006 to 2015.

Ramanathan has received numerous awards for his outstanding contributions to the film industry. His accolades include the Tamil Nadu State Film Awards, such as the M.G.R. Award in 1996 and the Best Actor Award for Natpukkaga and Simmarasi in 1998. He has also won multiple Filmfare Awards South, including Best Tamil Actor Awards for Suryavamsam in 1997 and Natpukkaga in 1998.

In addition, he received several Cinema Express Awards, including the Best Villain Award for Pulan Visaranai in 1990 and the Best Actor Award for Suryavamsam in 1994. He was honoured with the Chevalier Sivaji Ganesan Award in 2000 and the Sivaji Ganesan Award in 2005.

Ramanathan was also felicitated with the Asianet Special Jury Award, the Jai Hind Patriotic Pride Award, and the Incisive Charisma Award by WE Magazine.