C.S. Lewis’s first name was Clive. His full birth name was Clive Staples Lewis, although he became widely known by his initials rather than his given name.
Lewis was born in Belfast, Ireland, in 1898. The middle name “Staples” came from his mother’s family, and “Lewis” was his surname. As a child, he adopted the nickname “Jack,” which remained his preferred name among friends and colleagues for most of his life.
The initials can cause confusion because readers sometimes assume that “C.S.” stands for Charles or Christopher. It does not. Lewis used “C.S. Lewis” professionally as an author, scholar, and Christian apologist, while people close to him generally called him Jack. The combination of a formal pen name and an informal nickname is one reason biographical accounts often identify him in several different ways.
Lewis later became famous for The Chronicles of Narnia, works of literary criticism, and books such as Mere Christianity and The Screwtape Letters. His first name is a small but useful key to distinguishing the author from fictional characters and similarly named writers.