What was C.S. Lewis’s full first name, revealed by the initials in his name?

C.S. Lewis’s full first name was Clive Staples.

He was born Clive Staples Lewis in Belfast, Ireland, on 29 November 1898. “Clive” was the name he used in official records, while friends and family generally called him “Jack,” a nickname he adopted during childhood.

The initials “C.S.” became internationally familiar through his books on Christianity, literary criticism, fantasy, and science fiction. The middle name “Staples” came from his mother’s family name and was also used by his brother Warren.

Lewis is sometimes mistakenly given names beginning with Charles or Christopher because the initials are widely recognized but less often expanded. His published works normally used the initials rather than the full name, making “Clive Staples” a useful biographical detail.