At which university did J.R.R. Tolkien serve as a professor and spend most of his academic career?

J.R.R. Tolkien served as a professor at the University of Oxford and spent most of his academic career there. He held several Oxford teaching and research posts, beginning at Pembroke College and later continuing at Merton College.

At Pembroke, Tolkien was Rawlinson and Bosworth Professor of Anglo-Saxon from 1925 until 1945. He then became Merton Professor of English Language and Literature, a position he held from 1945 until his retirement in 1959.

Oxford provided the setting for much of Tolkien’s scholarly work and for important friendships. He was a member of the informal literary group known as the Inklings, which included C.S. Lewis. Tolkien’s academic specialization in Old and Middle English strongly influenced his invented languages, names, and imagined histories.

Tolkien did attend Exeter College, Oxford, as a student, and that can make the answer sound like a college rather than a university. Exeter was his Oxford college; the institution in which he taught was the University of Oxford.