What language did J.R.R. Tolkien study in the Old English poem Beowulf?

J.R.R. Tolkien studied Beowulf as a work written in Old English.

Beowulf is an Old English epic poem preserved in a manuscript dating from around the year 1000. Tolkien was a leading philologist and taught Old English at Oxford, making the poem a central part of his academic field.

In 1936 he delivered the influential lecture “Beowulf: The Monsters and the Critics.” The lecture argued that the poem should be valued as a coherent work of art, not merely as a source of historical information about Anglo-Saxon life.

Tolkien's interest in Beowulf also influenced his fiction. Dragons, heroic struggles, treasure, and ancient northern legends appear in both the poem and Tolkien's imaginative world, though Beowulf is not a Middle-earth story.