who's who

American  

noun

1. a reference work containing short biographical entries on the outstanding persons in a country, industry, profession, etc..

   a who's who in automotive engineering.

2. the outstanding or influential persons in a community, industry, profession, or other group.

   The who's who of racing will be there.

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who's who British  

noun

1. a book or list containing the names and short biographies of famous people

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who's who Idioms  

1. The outstanding or best-known individuals of a group, as in Tonight's concert features a veritable who's who of musicians. This expression comes from the name of a famous reference work, Who's Who, first published in 1849, which contains biographical sketches of famous individuals and is regularly updated. Its name in turn was based on who is who, that is, the identity of each of a number of persons, a phrase dating from the late 1300s. [Early 1900s]

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Etymology

Origin of who's who

First recorded in 1840–50

Example Sentences

The dinner brings together journalists and the who's who of Washington to raise funds for scholarships and awards.

From Barron's • Apr. 26, 2026

In the comments section of Skylight’s post announcing the big news, the who’s who of L.A.’s literati popped the proverbial champagne.

From Los Angeles Times • Apr. 16, 2026

Kelly: We've also had a fair few people talk about being at your 40th birthday in January and it was like a who's who of football...

From BBC • Mar. 21, 2026

A who's who of cricket greats have posted messages of support, including former England skipper Michael Vaughan and Indian legends Ravichandran Ashwin and VVS Laxman.

From Barron's • Jan. 2, 2026

I mean, everyone’s smiling and laughing and trying to guess who’s who behind what mask.

From "Free Lunch" by Rex Ogle