C.S. Lewis’s surname before he married Joy Davidman was Lewis.
C.S. Lewis was born Clive Staples Lewis and used Lewis as his family surname throughout his public career. He married the American writer Joy Davidman in a civil ceremony in 1956, so his surname did not change before that marriage. They later received a Christian marriage ceremony at Oxford’s Church of England parish church in 1957.
The wording of this fact can create confusion because Davidman was previously married to William Lindsay Gresham, and she had two sons, Douglas and David. Lewis became their stepfather after his relationship with Davidman developed.
Lewis’s marriage to Joy Davidman lasted only a few years because she died of cancer in 1960. He later described the experience of grief in A Grief Observed, published in 1961 under the pseudonym N.W. Clerk. Lewis himself died in 1963.