Katie is the English pet form of Katherine, which goes back to the Greek Aikaterine and has long been associated with katharos, "pure". It has been used as a name in its own right since the 19th century, and swimmer Katie Ledecky is one of its best-known American bearers today. Katie was number 95 in the United States in 2000, 307 in 2015 and ranks 646 among girls' names in 2025.