The Grimm tale “The Frog Prince” is assigned Aarne-Thompson type AT 440.
AT 440 is the traditional Aarne-Thompson classification for “The Frog King,” the tale type represented by the Grimm story commonly known in English as “The Frog Prince.” The Grimm version carries the fuller title “The Frog King, or Iron Heinrich.”
The story was published in 1812 in the first volume of Kinder- und Hausmärchen and is traditionally placed as the collection’s opening tale. Its plot centers on a princess’s encounter with a frog who has helped recover her golden ball and demands a promise in return.
AT numbers classify recurring folktale plots rather than individual books or characters. That is why similar frog-suitor stories from other regions may share the same type number. AT 440 should also not be confused with ATU classifications that were revised or expanded after the original Aarne-Thompson system.