Mitanni was a very long time ago. There were people who lived in a place called Mitanni a really, really long time ago. They lived in a place that is now in the countries of Syria and Iraq.
These people were really good at fighting and they had a lot of big horses that they could ride into battle. They were friends with another group of people called the Hittites. They were so close with the Hittites that they would even marry each other's princesses and princes, which is like being friends with someone so much that you become part of their family.
Even though they were friends with the Hittites, they also fought against them sometimes because they wanted to be in charge of their own land. Eventually, the Mitanni people disappeared and no one really knows why. But we can still learn a lot about them from the things they left behind, like statues and writing on clay tablets.