King Matt the First is a children's novel published in 1923 by Polish author, pediatrician, and child pedagogue Janusz Korczak. In addition to telling the story of a young king's adventures, it describes many social reforms, particularly targeting children, some of which Korczak enacted in his own orphanage, and is a thinly veiled allegory of contemporary and historical events in Poland. The book has been described as being as popular in Poland as Peter Pan was in the English-speaking world.