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

As for the presenters, it's a who's who of famous names, led by none other than Paddington Bear.

From BBC • Feb. 21, 2026

Dunkin’ and endorser Ben Affleck, meanwhile, generated more engagement than any other celebrity spot by casting its “Good Will Hunting” parody with a who’s who of hit ’90s sitcoms including “Friends,” “Seinfeld” and “Family Matters.”

From The Wall Street Journal • Feb. 9, 2026

That list reads like a who's who of showbiz, from composers Richard Rodgers and Alan Menken to actresses Audrey Hepburn and Whoopi Goldberg to singers John Legend and Jennifer Hudson.

From Barron's • Feb. 2, 2026

And he brought together a who’s who of business leaders, politicians and generals to advise the bank on the “Security and Resiliency Initiative.”

From The Wall Street Journal • Dec. 8, 2025

“How do you know who’s who if they don’t smell?”

From "The One and Only Ivan" by Katherine Applegate