What was C.S. Lewis's birth name before he adopted his pen name?

C.S. Lewis was born Clive Staples Lewis on 29 November 1898 in Belfast, Ireland. The initials “C.S.” came directly from his first and middle names, while “Lewis” was his family surname.

As a child, Lewis was called “Jack” by family and friends. The nickname arose from his affection for a childhood dog named Jacksie and remained his preferred everyday name for most of his life. He did not legally change his name to Jack; it was an informal identity.

Lewis later became known publicly as C.S. Lewis through his books, essays and lectures. “C.S.” is sometimes mistakenly expanded as “Charles Staples” or “Christopher Lewis,” but both are incorrect. His full baptismal name was Clive Staples Lewis, a fact recorded in biographies and archival references.

Lewis’s unusual combination of formal initials and the friendly nickname Jack reflects the distinction between his public literary career and private life. He used the initials consistently on title pages, including those of The Chronicles of Narnia.