Geert van wanrooij was a Dutch illustrator. He has made illustrations for several children's books, like the series 'Boeiende verhalen' by M. Cajetenus Berends between 1948 and 1953. He illustrated several books for Het Boekhuis in Antwerp and St. Gregoriushuis in Utrecht, as well as the award-winning book 'Het Hartje uit Fantasia' by Margareta Lamend.
Van Wanrooij drew the comic strip 'De nieuwste avonturen van Jan Klaassen', with captions in rhyme by journalist Frans Otten, for the regional newspaper Noordhollands Dagblad in 1947. The story was collected in a booklet by Bonnevile in Bergen in 1997.