The traditional wooden fan carried by a sumo referee is called a gunbai.
A gunbai is a military-style signaling fan used by the gyōji, the referee who officiates a professional sumo bout. During the match, the gyōji holds the fan and points it toward the side judged to have won. The direction indicates the winner’s side of the ring rather than serving as a simple decorative gesture.
The referee’s decision can be challenged by the ringside judges, who are senior sumo figures. If they call a mono-ii, or ringside conference, they review the result and may uphold or overturn the gyōji’s ruling. The final decision therefore does not always rest with the person holding the gunbai.
Gunbai are also associated with Japanese military and ceremonial traditions. In sumo, the fan is one of the most recognizable visual symbols of the gyōji’s role, alongside the referee’s distinctive clothing, hat, and formal calls during the bout.