Sumo is a Japanese form of wrestling that has been practiced since ancient times. It is a popular spectator sport in Japan and is considered a national sport. SUMO wrestlers, or rikishi, compete in a circular ring, called a dohyo, and attempt to force their opponent out of the ring or onto the ground. The rules of SUMO are complex and the matches can be quite intense. SUMO is an important part of Japanese culture and is often used as a metaphor for life.