Vaali ,born T. S. Rangarajan is a Tamil poet and lyricist who writes Tamil language poetry and film song lyrics. Most recently he has written a song Kallai Mattum in Dasavatharam for the music of Himesh Reshamiyya. He has also acted in a couple of films most notably, Hey Ram and Parthale Paravasam. He was recently nominated for Padma Shri for his literary work.

Vaali, whose real name is Rangarajan, was born in an Iyengar family at Srirangam in 1931. His father's name is Srinivasa Iyengar and his mother is Ponnammal. He was an artist and he worked at All India Radio (AIR). He holds the record for having written most number of lyrics in Tamil. He has written lyrics for hundreds of songs. He is a prolific writer as well; he has written books like Avathara Purushan, Pandavar Bhoomi, Ramanuja Kaviyam, Krishna Vijayam, Kalaignar Kaviyam, Krishna Bhakthan and Naanum Indha Nootrandum.

He was adept in painting, which inspired his friends to give him the name "Vaali".

Vaali has not only written lyrics in pure Tamil, but all sorts of folk, hip-hop, rhythm and blues as well. He has also mixed other languages in Tamil songs. The legend goes that Vaali at one time in his life was contemplating suicide due to immense poverty when he heard the lines of the song "Mayakkama Kalakkamma" from the movie SumaiThangi, penned by Kannadasan. The lines "Unakkum keezhey ullavar kodi ninaithu paarthu nimmadhi naadu..." changed his mindset and renewed his determination to live a new life. He has said that there were once 24 hours but no food to eat and next came a time when he had enough on the plate but no time to eat.

Actor Kamal Haasan had asked Vaali to pen the lyrics for a love song for the film Apoorva Sakotharargal. Kamal asked him specifically to pen a love failure song. Vaali penned the lyrics and gave them to him. But Kamal wasn't satisfied as he felt the depth of emotion conveyed through the lyrics failed to match the intensity of the situation in the film