Clive Staples Lewis (November 29, 1898 – November 22, 1963), commonly referred to as C. S. Lewis and known to his friends and family as "Jack," was an Irish  novelist, poet, academic, medievalist, literary critic, essayist, lay theologian and Christian apologist. Lewis was a prolific writer, and his circle of literary friends became an informal discussion society known as the "Inklings", including J. R. R. Tolkien, Nevill Coghill, Lord David Cecil, Charles Williams, Owen Barfield, and his brother Warren Lewis.

Born in Belfast, Lewis was schooled by private tutors before being sent to the Wynyard School in Watford, Hertfordshire, in 1908, just after his mother's death from cancer. The school was closed not long afterwards due to a lack of pupils. Lewis then attended Campbell College in the east of Belfast about a mile from his home, but he left after a few months due to respiratory problems. He was then sent to the health-resort town of Malvern, Worcestershire, where he attended the preparatory school Cherbourg House, which Lewis calls "Chartres" in his autobiography. It was during this time that Lewis abandoned his childhood Christian faith and became an atheist, becoming interested in mythology and the occult. In September 1913, Lewis enrolled at Malvern College, where he remained until the following June. After leaving Malvern he studied privately with William T. Kirkpatrick, his father's old tutor and former headmaster of Lurgan College.  In 1916, Lewis was awarded a scholarship at University College, Oxford.

In 1917, Lewis left his studies to volunteer in the British Army. During World War I, he was commissioned an officer in the Third Battalion, Somerset Light Infantry. Lewis arrived at the front line in the Somme Valley in France on his nineteenth birthday, and experienced trench warfare.  On April 15, 1918, Lewis was wounded.  Upon his recovery in October, he was assigned to duty in Andover, England. He was discharged in December 1918, and soon returned to his studies. Lewis received a First in Honour Moderations (Greek and Latin Literature) in 1920, a First in Greats (Philosophy and Ancient History) in 1922, and a First in English in 1923.

Lewis then taught as a fellow of Magdalen College, Oxford, for nearly thirty years, from 1925 to 1954, and later was the first Professor of Medieval and Renaissance English at Cambridge University and a fellow of Magdalene College, Cambridge. Much of his scholarly work concentrated on the later Middle Ages, especially its use of allegory. His The Allegory of Love (1936) helped reinvigorate the serious study of late medieval narratives like the Roman de la Rose.

In addition to his scholarly work, Lewis wrote a number of popular novels, including his science fiction The Space Trilogy and his fantasy fiction for children, The Chronicles of Narnia books, most dealing implicitly with Christian themes such as sin, humanity's fall from grace, and redemption.  Before Lewis's conversion to Christianity, he published two books: Spirits in Bondage, a collection of poems, and Dymer, a single narrative poem. Both were published under the pen name Clive Hamilton.  His first novel after becoming a Christian was The Pilgrim's Regress (1933), which depicted his experience with Christianity in the style of John Bunyan's The Pilgrim's Progress. Lewis wrote several works on Heaven and Hell including The Great Divorce and The Screwtape Letters. Lewis's last novel was Till We Have Faces, which he thought of as his most mature and masterly work of fiction but which was never a popular success.