In sociology and psychology, mass hysteria (also known as collective hysteria, group hysteria, or collective obsessional behavior) is a phenomenon that transmits collective delusions of threats, whether real or imaginary, through a population in society as a result of rumors and fear. In medicine, the term is used to describe the spontaneous manifestation of the same or similar hysterical physical symptoms by more than one person.

Mass Hysteria is a French heavy metal band formed in 1993 that released six albums between 1997 and 2009. Their breakthrough came in 1999 with their second album Contraddiction.