The term "Who's Who" primarily refers to a reference work or publication that lists biographical information about notable and influential people, often within a particular field or country. The most famous example is the British Who's Who , published annually since 1849, which includes autobiographical entries of prominent living individuals who impact British life. It provides details such as education, career, and sometimes personal information, typically supplied by the individuals themselves

. There are many national and specialized versions of Who's Who , such as Who's Who in America (since 1899), Canadian Who's Who , Who's Who in Australia , and others covering various countries and fields

. These works serve as accessible sources for biographical data on distinguished persons. Additionally, "Who's Who" can also mean a list or group of notable people in a particular context, such as an event or organization, often used idiomatically to indicate the presence of many important figures

. In a different context, "Who's Who" is also the name of a character in the manga and anime One Piece , who is a member of the Beasts Pirates

. In summary, "Who's Who" is best known as a biographical reference publication listing prominent individuals, but the phrase can also refer to notable groups or specific characters in popular culture depending on context.