Wikipedia
Ramavataram, popularly referred to as Kamba Ramayanam, is a Tamil epic that was written by the Tamil poet Kamban during the 12th century. Based on Valmiki's Ramayana (which is in Sanskrit), the story describes the life of King Rama of Ayodhya. However, Ramavatharam is different from the Sanskrit original in many aspects - both in spiritual concepts and in the specifics of the storyline. This historic work is considered by both Tamil scholars and the general public as one of the greatest literary works in Tamil literature.
Kamban wrote this epic with the patronage of Thiruvennai Nallur Sadayappa Vallal, a Pannai kula chieftain (திருவெண்ணை நல்லூர் சடயப்ப வள்ளல்). In gratitude to his patron, Kamban references his name once in every 1,000 verses.
The epic is quite well known, both in the Tamil literary world and in the Hindu spiritual world, for the colorfulness of its poetry and for its religious value.