Sumo is first mentioned in a Japanese book more than a thousand years ago, but experts believe it might be much older.
There are also ancient wall paintings showing the sport, so sumo might even have been played by prehistoric man praying for a good harvest.
Centuries later it was used by soldiers and warriors against their enemies and it was also used by ordinary people in street-fighting before it was banned for being too dangerous.
Although sumo is one of the world's oldest sporting activities, it's not just a sport. It's more a way of life and it has played an important role in Japan's cultural and religious history.
In Japan wrestlers are seen as role models and heroes for many people. They're looked up to like footballers are in the UK.