C.S. Lewis publicly became a Christian in 1931 after his earlier atheism.
Lewis had moved from childhood Christianity to atheism during his adolescence. His return to belief developed gradually through reading, philosophical reflection, and conversations with fellow writers. Important influences included Owen Barfield and J.R.R. Tolkien, both of whom challenged his assumptions about myth, reason, and Christianity.
Lewis described himself as converting to theism in 1930 and then returning to Christianity in 1931. His conversion became a central fact in biographies because it shaped the apologetic books, essays, radio talks, and fiction that followed.
The exact wording of “conversion” can create confusion because Lewis described stages rather than one instantaneous event. His later account in Surprised by Joy presents the process autobiographically, but the date most commonly given for his conversion to Christianity is 1931. This was before the publication of most of his best-known Christian works.