Llyfr Aneirin (‘The Book of Aneirin’) is one of the Four Ancient Books of Wales. It is a relatively small medieval manuscript of 38 pages containing an unique text of what may be the earliest surviving Welsh literature. The Book of Aneirin is an ancient poem called the Gododdin, a series of eulogies to brave warriors from Gododdin who fought and died to take their land back from invaders in Catraeth.