The Old English poem Tolkien translated and annotated for a 2014 publication is Beowulf.
Beowulf: A Translation and Commentary was edited by Christopher Tolkien and published in 2014, decades after J.R.R. Tolkien's death. It presents Tolkien's prose translation of the Old English epic together with his commentary and a related poem, Sellic Spell.
Tolkien was a distinguished Beowulf scholar. His 1936 lecture “Beowulf: The Monsters and the Critics” helped reshape modern academic discussion by arguing that the poem should be valued as a work of art rather than treated merely as historical evidence.
The poem tells of the hero Beowulf's battles with Grendel, Grendel's mother, and a dragon. It is not a Tolkien invention, although Tolkien's fiction contains echoes of its heroic atmosphere, monsters, treasure, and doomed northern world. His translation is therefore a scholarly engagement with an older English literary tradition.