Middle-earth is a place in a story called "The Lord of the Rings". It's a world just like ours, but there are magical creatures like hobbits, elves, and dwarves. The story is about a hobbit named Frodo who has to go on a big journey to destroy a powerful ring that an evil guy called Sauron wants to use to control the world. Along the way, Frodo meets lots of cool characters and goes to really interesting places like Rivendell, the Mines of Moria, and Mordor. Middle-earth is a made-up world, but it's so detailed and interesting that lots of people love to read about it and watch movies about it.