A ringmaster or ringmistress, or sometimes a ringleader, is a significant performer in many circuses. Most often seen in traditional circuses, the ringmaster is a master of ceremonies that introduces the circus acts to the audience. In smaller circuses, the ringmaster is often the owner and artistic director of the circus.

A circus is a company of performers who put on diverse entertainment shows that may include clowns, acrobats, trained animals, trapeze acts, musicians, dancers, hoopers, tightrope walkers, jugglers, magicians, ventriloquists, and unicyclists as well as other object manipulation and stunt-oriented artists. The term circus also describes the field of performance, training and community which has followed various formats through its 250-year modern history. Although not the inventor of the medium, Newcastle-under-Lyme born Philip Astley is credited as the father of the modern circus.