The Frog Princess is a fairy tale that has multiple versions with various origins.
Russian variants include the Frog Princess or Tsarevna Frog (Царевна Лягушка, Tsarevna Lyagushka) and also Vasilisa the Wise (Василиса Премудрая, Vasilisa Premudraya); Alexander Afanasyev collected variants in his Russian Folk Tales. Andrew Lang included an Italian variant titled The Frog in The Violet Fairy Book.Italo Calvino included another Italian variant from Piedmont, The Prince Who Married a Frog, in Italian Folktales, where he noted that the tale was common throughout Europe. Georgios A. Megas included a Greek variant, The Enchanted Lake, in Folktales of Greece.
It is classified as type 402, the animal bride, in the Aarne–Thompson index. Another tale of this type is Doll i' the Grass.
The king (or an old peasant woman, in Lang's version) wants his three sons to marry. To accomplish this, he creates a test to help them find brides. The king tells each prince to shoot an arrow. According to the King's rules, each prince will find his bride where the arrow lands. The youngest son's arrow is picked up by a frog. The king assigns his three prospective daughters-in-law various tasks, such as spinning cloth and baking bread. In every task, the frog far outperforms the two other lazy brides-to-be. In some versions, the frog uses magic to accomplish the tasks, and though the other brides attempt to emulate the frog, they cannot perform the magic. Still, the young prince is ashamed of his frog bride until she is magically transformed into a human princess.
In Calvino's version, the princes use slings rather than bows and arrows. In the Greek version, the princes set out to find their brides one by one; the older two are already married by the time the youngest prince starts his quest. Another variation involves the sons chopping down trees and heading in the direction pointed by them in order to find their brides.