Aneurin or Aneirin, fl. c.600, Welsh bard whose reputed writings are contained in a 13th-century manuscript, The Book of Aneirin. Included in this manuscript is Y Gododdin, an elegiac poem of about 1000 lines recording the defeat of an army of northern Britons by the Saxons. The poem is one of the oldest extant works of Welsh literature and contains probably the earliest explicit allusion to King Arthur.