Beowulf is an Old English heroic epic poem. It is not known who wrote it, and there is no agreement as to when it was written. Estimates for the date range from AD 608 right through to AD 1000, and there is no consensus. The poem has only one manuscript source, written about 1010. "Beowulf" is 3182 lines long. Tolkien describes and illustrates many of the features of Old English poetry in his 1940 essay "On translating Beowulf".