C.S. Lewis publicly embraced Christianity in 1931.
Lewis’s conversion followed a long intellectual and personal movement away from atheism. He had returned to theism by 1930, influenced partly by conversations with friends including J.R.R. Tolkien and Hugo Dyson. Lewis described a decisive experience on 19 September 1931, when he traveled to Whipsnade Zoo with his brother Warren; he later wrote that he believed he was converted to Christianity that day.
The conversion did not make Lewis’s religious writing immediately simple or settled. He continued thinking carefully about theology, imagination, morality, and the relationship between myth and truth. His first major Christian book, The Pilgrim’s Regress, appeared in 1933.
Biographies sometimes distinguish between Lewis’s return to belief in God and his later acceptance of Christianity. He was no longer an atheist before 1931, but 1931 is the date commonly given for his conversion to Christianity. His faith later informed both his apologetic works and the symbolism of Narnia.