Clive Staples Lewis (29 November 1898 - 22 November 1963) was a British author, literary scholar, Christian apologist, and popular theologian whose work spans fiction, literary criticism, theology, and philosophy. Born in Belfast, Ireland (then part of the United Kingdom), Lewis spent most of his academic career at Oxford University and later at Cambridge University, where he held a Chair in Medieval and Renaissance Literature. He is best known to general audiences for the seven-volume fantasy series The Chronicles of Narnia and to theological audiences for works such as Mere Christianity, The Screwtape Letters, and The Problem of Pain. Lewis died on 22 November 1963, the same day as the assassination of U.S. President John F. Kennedy and the death of author Aldous Huxley.

Lewis was raised in a nominally Protestant household in Belfast, lost his mother to cancer at age nine, and had largely abandoned Christian belief by his teenage years. He served in the British Army during World War I and was wounded during the German Spring Offensive near Arras in April 1918. After the war he studied at University College, Oxford, earning first-class honors in Classics, Philosophy and Ancient History, and English Literature. He became a Fellow and Tutor in English at Magdalen College, Oxford in 1925, a post he held until 1954, when he accepted the newly created Chair of Medieval and Renaissance English at Magdalene College, Cambridge.

Lewis's return to theism, and subsequently to Christianity, occurred gradually during his late twenties and early thirties, and he described the process in his autobiographical work Surprised by Joy (1955). His friendship with J. R. R. Tolkien, a devout Catholic, is frequently cited as a significant influence on his reconversion, though Lewis remained Anglican rather than converting to Roman Catholicism. He was a founding member of the Inklings, an informal Oxford literary group whose other notable members included Tolkien and Charles Williams.

In his later years Lewis met Joy Davidman, an American poet and former Communist who had converted to Christianity; they married in 1956. Her death from cancer in 1960 prompted A Grief Observed, one of his most personal works.

His fiction output includes the Space Trilogy (also called the Ransom Trilogy), the allegorical novel The Pilgrim's Regress, and the posthumously completed The Dark Tower. His works of Christian apologetics and theology attracted both wide popular readership and substantial scholarly and ecclesiastical criticism. His academic work, particularly The Allegory of Love (1936) and English Literature in the Sixteenth Century, Excluding Drama (1954), is regarded by literary scholars as significant contributions to the field independent of his popular writing.

Lewis argued for the rational defensibility of Christian belief at a time when such arguments were unfashionable in British intellectual culture. His “trilemma” argument - that Jesus Christ must be understood as either Lord, liar, or lunatic, and that the liar and lunatic options are untenable - became one of the most widely discussed and contested arguments in popular apologetics. Critics have argued the trilemma omits the possibility that the Gospel accounts are legendary or mythologized rather than historically reliable. See the debate on the trilemma argument.

Lewis's treatment of suffering in The Problem of Pain and his later, more personal engagement with grief in A Grief Observed - written after the death of his wife Joy Davidman - present two notably different tonal registers on the same theological question. Some scholars treat these as complementary; others have argued they reflect tension or development in Lewis's own thinking. See viewpoints on Lewis's theodicy.

His literary criticism, particularly his advocacy for reading older texts on their own terms rather than through contemporary ideological frameworks, has been adopted by scholars across the political spectrum and is sometimes associated with what Lewis called “chronological snobbery” - the assumption that newer ideas are necessarily superior to older ones.

Lewis's popular theological works, particularly Mere Christianity and The Screwtape Letters, have remained continuously in print and are frequently cited by converts to Christianity, particularly in Evangelical and Anglican contexts. His work is less frequently cited in Roman Catholic or Eastern Orthodox apologetics, though he has readers in both traditions. Academic reception of his fiction has been mixed; The Chronicles of Narnia in particular has attracted criticism for its allegorical Christian content and for depictions that some readers characterize as sexist or racially insensitive by contemporary standards. See the debate on Narnia's legacy.

Lewis's reputation in academic literary studies has fluctuated. His championing of older literature and his open Christianity placed him somewhat outside mainstream mid-twentieth-century literary criticism. Reassessments since his death have tended to treat his scholarly and popular work more separately.

• C. S. Lewis - History
• C. S. Lewis - Trilemma Debate
• C. S. Lewis - Theodicy Viewpoint
• C. S. Lewis - Narnia Debate
• Christian Apologetics
• The Inklings
• Mere Christianity
• The Chronicles of Narnia

1. Walter Hooper, C. S. Lewis: A Complete Guide to His Life and Works (HarperCollins, 1996).
2. Alister McGrath, C. S. Lewis - A Life: Eccentric Genius, Reluctant Prophet (Tyndale House, 2013).
3. C. S. Lewis, Surprised by Joy (Geoffrey Bles, 1955).
4. C. S. Lewis, Mere Christianity (Geoffrey Bles, 1952).
5. C. S. Lewis, The Allegory of Love (Oxford University Press, 1936).
6. Humphrey Carpenter, The Inklings (George Allen & Unwin, 1978).
7. C. S. Lewis, A Grief Observed (Faber and Faber, 1961).