Thalai Nagaram (transl. Capital city) is a 2006 Indian Tamil-language action crime film written and directed by Suraj and produced by V. Ravichandran. The film stars Sundar C in his lead acting debut and Jyothirmayi, while Vadivelu, Prakash Raj, Judo. K. K. Rathnam, K. S. Ravikumar, and Bose Venkat play supporting roles. This film was a low-budget production but enjoyed huge success. The soundtrack, composed by D. Imman, was a great hit, and the song "Yedho Ninaikiren" charted at the top position for a week. The film also has cinematography by K. S. Selvaraj and editing by Mu. Kasi Viswanath.

The film is a remake of the Malayalam film Abhimanyu, directed by Priyadarshan and starring Mohanlal. The film tells the story of a man who sacrifices his life to kick out gangsters who ruin other's lives.

The film was followed by Naai Sekar Returns (2022), a comedy spin-off of Vadivelu's character in the film, and a standalone sequel Thalainagaram 2(2023).