Badass: A Relentless Onslaught of the Toughest Warlords, Vikings, Samurai, Pirates, Gunfighters, and Military Commanders to Ever Live, also known as Badass: The Book, is a history and biography book.

It is the debut book of Ben Thompson, owner of the website Badass of The Week.

The book focuses on historical figures considered to be badass: having exceptional toughness, aggressiveness, battle skills and/or resilience, and have a significant achievement or impact on history.

Thompson has stated in an interview that he intended to convey history in the language of youth, so that they feel like "reading something [they're] not supposed to, but ... actually learning something.

The illustrations are done by several artists that have done work for Wizards of the Coast, White Wolf, and DC Comics.