Who Was...?

Who Was? or Who HQ is a series of children's non-fiction books published by Penguin Books. The "Who Was...?", "What Was?...", "Where Is?...", "What Is the Story Of?...", "What Do We Know About?..." and "Who HQ Now" series tell the stories of trailblazers, legends, innovators, significant landmarks, and historical events. Covering everything from sports to politics, the "Who HQ Now" series focuses on trending topics and prominent subjects discussed in the news. As of December 2022, the series had over 250 entries, sold over 20 million copies, and has been on the New York Times Best Seller list.

The first four Who Was? books — Who Was Sacagawea?, Who Was Ben Franklin?, Who Was Albert Einstein?, and Who Was Annie Oakley?—were published on February 18, 2002. Penguin Books publishes about 24 new books each year. Example entrants in the series due for publication in 2025 include Tony Hawk, Carol Burnett, Willie Nelson, Wilma Mankiller, Caitlin Clark, Shohei Ohtani, the story of Cinderella, the Renaissance, Tornado Alley and more.