What was Tolkien’s academic field of expertise?

Tolkien’s academic field of expertise was philology.

Philology is the historical study of language and literature, especially through texts. Tolkien trained in the study of languages and medieval works, including Old English, Middle English, Old Norse, Welsh, Finnish, and Gothic. This background shaped his approach to invented languages and fictional history.

He was a professor at Oxford and wrote influential scholarship on works such as Beowulf and Sir Gawain and the Green Knight. His 1936 essay Beowulf: The Monsters and the Critics argued that the poem’s monsters were central to its meaning and artistic design.

Tolkien’s fiction is not simply a collection of invented words. He built relationships between languages, dialects, writing systems, names, and historical periods. That philological method helped give Middle-earth the depth of a remembered world, with peoples whose languages changed over time.