Mo Willems (born February 11, 1968 in Des Plaines, IL) is an American writer, animator and creator of children's books.
Willems started his career as a writer and animator for Sesame Street, where he earned six Emmy Awards for writing during his tenure from 1993 to January 2002. He then created the KaBlam! short The Off-Beats, where it ran on the show's first two seasons. Willems went to Cartoon Network to create Sheep in the Big City, where it was a success with the critics but ultimately failed to attract sufficient viewership and was canceled after two seasons.
He later worked as head writer on the first four seasons of Codename: Kids Next Door, created by one of his colleagues from Sheep in the Big City, Tom Warburton. He left the show to pursue his writing career.
Three of Willems' books have been awarded a Caldecott Honor: Don't Let the Pigeon Drive the Bus! (2004), Knuffle Bunny: A Cautionary Tale (2005), and Knuffle Bunny Too: A Case of Mistaken Identity (2008). Recently he has been creating the Elephant and Piggie books, an early reader series about a friendly elephant and pig. Those books won the Theodor Seuss Geisel Medal in 2008 and 2009, and Geisel Honors in 2011, 2012, 2013, 2014 and 2015. In 2010, Willems introduced a new series of books featuring Cat the Cat, also aimed at early readers.
Mo Willems currently resides in Massachusetts with his wife and their daughter Trixie.