Which 1925 poem did J.R.R. Tolkien edit with E. V. Gordon?

J.R.R. Tolkien edited Sir Gawain and the Green Knight with E. V. Gordon.

Their scholarly edition was published in 1925 and presented the Middle English poem with an introduction, notes, and a glossary. The work helped establish Tolkien’s reputation as a specialist in medieval English language and literature before his best-known fiction appeared.

Sir Gawain and the Green Knight tells of Sir Gawain, a knight of King Arthur’s court, who accepts a strange beheading challenge from the Green Knight. The poem’s themes of courage, courtesy, temptation, and the limits of human virtue resonated with Tolkien’s scholarly interests, though it is not a story set in Middle-earth.

Tolkien also wrote and lectured extensively on Beowulf, and he translated or studied several other medieval texts. That broader body of work can make titles easy to mix up. The distinctive 1925 collaborative edition with Gordon, however, concerned Sir Gawain and the Green Knight.