The traditional referee in a professional sumo bout is called a gyoji. The gyoji enters the dohyo in distinctive ceremonial clothing, announces the wrestlers, calls the start, and indicates the winner with a war fan called a gunbai.
Gyoji also help prepare tournament schedules and perform other administrative duties. Their ranks are signaled by details of their clothing, and the highest-ranking referee officiates the top bouts.
Gyoji decisions can be challenged by the shimpan, the five ringside judges who monitor the action. If the judges believe the referee’s ruling is incorrect, they may confer and overturn it. Thus, the gyoji is the visible bout referee, while shimpan provide a review function.