What was C.S. Lewis’s Christian name at birth?

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

He was born Clive Staples Lewis on 29 November 1898 in Belfast. The initials “C.S.” came from his given names, Clive Staples, rather than from a pen name or abbreviated title. In private life, however, Lewis was commonly known as “Jack.”

The nickname began after a childhood incident involving a dog called Jacksie. After the dog was killed, Lewis reportedly adopted the name Jacksie and later shortened it to Jack. His family and close friends continued using Jack for much of his life, while his published works appeared under C.S. Lewis.

The name “Clive Staples Lewis” is sometimes mistaken for a formal middle-name expansion invented by publishers. It was his actual birth name. The initials became closely associated with books ranging from The Chronicles of Narnia to The Problem of Pain and Mere Christianity, making the distinction between his public and private names a useful biographical detail.