Isai (transl. Music) is a 2015 Indian Tamil-language musical psychological thriller film co-produced, written, directed and composed by S. J. Suryah, making his comeback as a director after a 10-year hiatus since 2005. The film stars himself in the lead role with debutant Sulagna in a female lead and Sathyaraj as the main antagonist. The story is about the tiff between Vetriselvan (Sathyaraj) and A. K. Shiva (Surya), the two music composers in the film industry. The film marked the debut of S. J. Surya, as a music director, with cinematography handled by Soundararajan and editing by K. M. Riyas.

The project was announced on 2004, after the release of New, with other two projects, which failed to materialize, and the film went on floors from 25 May 2012. The film which is touted to be of a new genre musical-thriller, released on 30 January 2015, to positive reviews from critics and ended up as hit at the box office.