Parable (allegory), Fable, Fantasy
The Little Prince can hop in and out of several genres. First off, the back cover of Shmoop’s copy of The Little Prince describes this book as a parable. According to Shmoop’s Literature Glossary, a parable is a short, didactic tale meant to convey a moral lesson. The book’s moral ideas are probably most clearly explained in the chapter in which the prince talks to the fox about seeing with the heart, learning about taming/friendship, and figuring out what really matters; however, little tips about how to live a more meaningful life are sprinkled throughout this book.
It’s not much of a stretch to move from the idea of parable into the idea of allegory, which is a story with two levels of meaning. This makes sense when we think about all the grown-ups the prince meets on his travels, each of them defined by his profession, and each of them helping the prince figure out a truth about how to see the world. (For more, check out “Symbols, Imagery, Allegory: The Little Prince as Allegory” and then come back.)
Finally, because the animals and flowers in this book talk and teach the human characters about things that matter, you could also think of this story as a fable, which is a short tale that conveys a moral and usually features talking animals and inanimate objects. Alternatively, you could think of The Little Prince as a fantasy or science-fiction story in which an alien comes to Earth, communicates with all kinds of beings, and tells the narrator about his strange adventures.