The "Who Was...?" books comprise a series of illustrated biographies for children aged 8 to 11 published by Penguin Young Readers Group. The books feature important historical figures.
The books in the series were written and illustrated by a variety of authors and illustrators. Some categories of people featured include movie directors, scientists, political leaders, writers and civil rights activists. Through a readers survey conducted in 2014, Steven Irwin was chosen to be the subject of the 100th "Who Was...?" book. The "Who Was...?" series is accompanied by a series of books entitled "What Was...?" that give accounts of important historical events.