William Sherman "Billy" Pène du Bois (May 9, 1916 - February 5, 1993) was an American writer and illustrator of books for young readers. He is best known for The Twenty-One Balloons, published in April 1947 by Viking Press, for which he won the 1948 Newbery Medal. As illustrator he was twice a runner-up for the Caldecott Medal. The Twenty-One Balloons is the work by Pène du Bois that WorldCat reports most widely held in participating libraries, by a wide margin. His other most widely held works are five books written by others, which he illustrated (below), and the two Caldecott Honor picture books, which he also wrote. From 1953 to 1960, Pène du Bois was art editor of The Paris Review, working alongside founder and editor George Plimpton.