Dancing mania (also known as dancing plague, choreomania, St John's Dance and St. Vitus' Dance) was a social phenomenon that occurred primarily in mainland Europe between the 14th and 17th centuries. It involved groups of people dancing erratically, sometimes thousands at a time. It affected men, women, and children, who danced until they collapsed from exhaustion. One of the first major outbreaks was in Aachen, Germany in 1374, and one particularly notable outbreak occurred in Strasbourg in 1518.
Dancing mania was well documented in contemporary reports, but poorly understood. There is no consensus among modern-day scholars as to the cause of it. Sources agree that dancing mania was one of the earliest-recorded forms of mass hysteria.