What was C.S. Lewis’s birth name, including the first name he later stopped using?

C.S. Lewis’s birth name was Clive Staples Lewis.

Lewis was born in Belfast, Ireland, on 29 November 1898. His parents named him Clive Staples Lewis, but he disliked the name Clive from childhood and later used “Jack” instead. Family and friends commonly called him Jack for the rest of his life.

The initials C.S. became the form used on his books and academic work. “Staples” was his mother’s maiden name, and Lewis used the initials rather than a shortened version of his first name. This is why readers may know the author almost exclusively as C.S. Lewis while biographical accounts call him Jack.

Lewis’s personal name is sometimes confused with his pen name or with the name of his brother, Warren Hamilton Lewis. Warren, usually called Warnie, was his older brother and later helped preserve records of Lewis’s life.