Karthik Sivakumar, better known by his stage name Karthi, is an Indian film actor, who works in the Tamil film industry. The younger son of actor Sivakumar, Karthi holds a Bachelor's degree in Mechanical Engineering and a Master's degree in Industrial Engineering. Since he had always wanted to become a film director, he returned to India and joined Mani Ratnam as an assistant director. He was offered acting roles and made his acting debut in Paruthiveeran in 2007 as the titular character, a careless village rowdy, winning critical acclaim and several accolades including the Filmfare Award for Best Actor and a Tamil Nadu State Film Award. His next role was that of a coolie in Aayirathil Oruvan, a fantasy-adventure film directed by Selvaraghavan. He achieved consecutive commercial successes with his subsequent releases – Paiyaa, Naan Mahaan Alla and Siruthai, which established him in the Tamil film industry.
Apart from his film career, Karthi has also been involved in social welfare activities, encouraging fans to do likewise through the "Makkal Nala Mandram", a social welfare club that he inaugurated. In 2011, he became a cause ambassador to promote awareness of lysosomal storage disease.