Which Oxford college did C.S. Lewis join as a fellow in 1925?

C.S. Lewis joined Magdalen College, Oxford, as a fellow in 1925. He was elected to a teaching fellowship in English at the college, beginning the Oxford phase of his academic career.

Lewis had studied at University College, Oxford, and later worked as a tutor before obtaining the Magdalen fellowship. At Magdalen, he taught English literature and developed the academic and social networks that supported much of his writing. His close friendship with J.R.R. Tolkien also grew during his Oxford years.

Magdalen College is different from the University of Oxford itself: the University is the larger institution, while Magdalen is one of its constituent colleges. Lewis remained at Magdalen until 1954, when he became the first holder of the English chair at Magdalene College, Cambridge. This question concerns his Oxford fellowship, not his later Cambridge professorship.