Ancient Thunder is a children's fantasy picture book by the Canadian artist and writer Leo Yerxa, simultaneously published in Canada and the United States in 2006. It won the 2006 Governor General's Award for Children's Illustration and the 2008 Saskatchewan Willow Award for picture books. Ancient Thunder was both illustrated and written by Leo Yerxa.

This book describes the relationship of horses and First Nation's cultures with a single poem and illustrations using water-colour artwork. Only few lines of text per page contrast with painted images associated with native culture.

Yerxa was interested by the native people while he watched them ride across the Great Plains in the movie when he was a child, their traditional clothing and the running creatures inspired Yerxa to write this book. He used handmade water-colour paper and made it look like leather.