Crockett Johnson (October 20, 1906 – July 11, 1975) was the pen name of the American cartoonist and children's book illustrator David Johnson Leisk. He is best known for the comic strip Barnaby (1942–1952) and the Harold series of books, beginning with Harold and the Purple Crayon. From 1965 until his death Johnson created over a hundred paintings relating to mathematics and mathematical physics. Eighty of these are found in the collections of the National Museum of American History.