Sumo was one of the Trial events that featured during the first and second series of Robot Wars. It was one of only two Trial events to feature in both series, the other being Football. It was designed as a test of a robot's brute strength and pushing power. Each robot would take turns to enter a small circular stage with one of the house robots, with the aim being to push the house robot out of the ring or otherwise remain on the stage for a full 60 seconds. The robot that survived for the least amount of time was eliminated from the competition. In the first series, the robots competed against Shunt and in the second series it was Shunt or Dead Metal.
- Robot Wars: The First Wars/Heat A
- Robot Wars: The Second Wars/Heat F
- Robot Wars: The Second Wars/Heat L
Sumo Basho returned as a side competition in The Fourth Wars. Shunt returned to face the competing robots. The winner of the event was Panic Attack, who dodged an attack by Shunt causing the house robot to fall out of the ring after 21 seconds. It was also planned to be a side competition in the Third Wars, but a behind the scenes accident caused it to be cancelled along with several other-weight class battles.