Who’s Who (or “Who is Who”) is the title of a number of reference publications, generally containing concise biographical information on a particular group of people. The title is also used as an expression meaning a collection or group of noted persons; as in the sentence, “The actors in the film were a Who’s Who of the great American comedians of the time”.
The title “Who’s Who” is in the public domain, and thousands of Who’s Who compilations of varying scope and quality have been published by various authors and publishers. The oldest and best known is the annual British publication Who’s Who, a reference work on contemporary prominent people. However, many publications using the title are vanity publications, where the inclusion criterion is the biographee’s willingness to buy the book, with the business model consisting of selling books directly to the biographees. These are widely considered to be Who’s Who scams.