Ringleader

Part of speech: noun (n.)

1. The leader of a circle of dancers; hence, the leader of a number of persons acting together; the leader of a herd of animals. A primacy of order, such an one as the ringleader hath in a dance. Barrow.

2. Opprobriously, a leader of a body of men engaged in the violation of law or in an illegal enterprise, as rioters, mutineers, or the like. The ringleaders were apprehended, tried, fined, and imprisoned. Macaulay.