The Ring Leader is a flying demon enemy from Final Fantasy IX. It can only be found on Terra. If its Virus Powder should cause a party member to contract a Virus, a Vaccine can be stolen to remedy the status.
The Japanese name for this enemy is the English phrase "Ring Commander", as the enemy commands a ring. The English localization uses the synonym "leader" in place of "commander". A ringleader is the leader of a group causing a disturbance, and also another name for a ringmaster in a circus.
In French it is named SdA, probably in reference to the book The Lord of the Rings (Seigneur des Anneaux).