Fantasio is a fictional character from the Spirou et Fantasio comic strip. He was introduced in 1944 by Jijé, who was then drawing Spirou's adventures. Fantasio is Spirou's best friend and co-adventurer, a graphic reporter with an uncontrolled imagination and a mop of blond hair. In his early incarnation, he was considerably taller than Spirou, with a clown-like demeanour, and his hairstyle resembled that of Blondie character Dagwood Bumstead. In the Franquin era, he and Spirou became more alike. He has an evil megalomaniac cousin, Zantafio, who is his sworn enemy but bears a strong physical resemblance to him.
Fantasio also appeared in the Gaston comic strip, where he was the main character's superior, often seen trying to sign contracts with Monsieur De Mesmaeker. In opposition to his role in Spirou, in Gaston Fantasio was a serious character, playing straight man to Gaston's goofy antics, who thus becomes to Fantasio what Fantasio is to Spirou. However, Fantasio left that series when André Franquin left Spirou et Fantasio after the album Panade à Champignac (taking Gaston and the Marsupilami with him), being replaced in the role by Léon Prunelle.