According to the present form of the tale (dating to the Edo period), Momotarō came to Earth inside a giant peach, which was found floating down a river by an old, childless woman who was washing clothes there. The woman and her husband discovered the child when they tried to open the peach to eat it. The child explained that he had been sent by Heaven to be their son. The couple named him Momotarō, from momo (peach) and tarō (eldest son in the family).
Years later, Momotarō left his parents to fight a band of marauding oni (demons or ogres) on a distant island. En route, Momotarō met and befriended a talking dog, monkey and pheasant, who agreed to help him in his quest. At the island, Momotarō and his animal friends penetrated the demons' fort and beat the band of demons into surrendering. Momotarō and his new friends returned home with the demons' plundered treasure and the demon chief as a captive. Momotarō and his family lived comfortably from then on.
Momotarō is strongly associated with Okayama, and his tale may have its origins there. The demon island (Onigashima (鬼ヶ島)) of the story is sometimes associated with Megijima Island, an island in the Seto Inland Sea near Takamatsu, due to the vast manmade caves found on that island.
The story has some regional variations. Some say Momotarō floated by in a box, a white peach or a red peach. Stories from Shikoku and Chugoku region muddy the distinction with characters from another folk story, the Monkey-Crab Battle, that Momotarō took with him allies to Oni Island, namely a bee (蜂 hachi), a crab (蟹 kani), a millstone (臼 usu), a chestnut (栗 kuri), and cow dung (牛の糞 ushi no fun).
There are variances about the Momotarō's process of growth; one is that he grew up to meet the expectation of the old couple to be a fine boy. Another is that he grew up to be a strong but lazy person who just sleeps all day and does not do anything. It is possible that the Momotarō being a fine boy version is more famous to give lessons to children. Nowadays, Momotarō is one of the most famous characters in Japan, as an ideal model for young kids for his kind-heartedness, bravery, power, and care for his parents.
Grown up, Momotarō goes on his journey to defeat the demons when he hears about the demons of the Onigashima (demon island). In some versions of the story, Momotarō volunteered to go help the people by repelling the demons, but in some stories he was forced by the townspeople or others to go on journey. However, all the stories describe Momotarō defeating the Oni and live happily ever after with the old couple.
The story has been translated into English many times. Rev. David Thomson translated it as the first volume of Hasegawa Takejirō's Japanese Fairy Tale series in 1885. Susan Ballard included it in Fairy Tales from Far Japan (1899). Yei Theodora Ozaki included it in her Japanese Fairy Tales (1911). Teresa Peirce Williston included it in Japanese Fairy Tales, Second Series, in 1911. And there are many other translations.
Inuyama, Japan, holds a festival called the Momotarō Festival at the Momotarō Shrine on May 5 every year.