Clive Staples "Jack" Lewis (29 November 1898 – 22 November 1963), commonly referred to as C. S. Lewis, was an Irish writer and scholar. Lewis is known for his work on medieval literature, Christian apologetics, literary criticism, and fiction. He is best known today for his series The Chronicles of Narnia.

Lewis was a close friend of J. R. R. Tolkien, the author of The Lord of the Rings. Both authors were leading figures in the English faculty at Oxford University and in the informal Oxford literary group known as the "Inklings". According to his memoir Surprised by Joy, Lewis had been baptised in the Church of Ireland at birth, but fell away from his faith during his adolescence. Owing to the influence of Tolkien and other friends, at about the age of 30, Lewis re-converted to Christianity, becoming "a very ordinary layman of the Church of England" . His conversion had a profound effect on his work, and his wartime radio broadcasts on the subject of Christianity brought him wide acclaim. Later in his life he married the American writer Joy Gresham, who died of bone cancer four years later at the age of 45.

Lewis's works have been translated into more than 30 languages and have sold more than a million copies per year. The books that comprise The Chronicles of Narnia have sold more than 100 million copies. Many stage and screen adaptations of Lewis's works have also been produced, the most notable of which is the 2005 Disney film adaptation of The Lion, the Witch and the Wardrobe.