Revolutionary spontaneity (also known as spontaneism) is a tendency to believe that social revolution can and should occur spontaneously from below, without the aid or guidance of a vanguard party, and that it cannot and should not be brought about by the actions of individuals or parties who might attempt to foment such a revolution.
In his work What is to be Done? (1902), Vladimir Lenin argued fiercely against revolutionary spontaneity as a dangerous "revisionist" concept that strips away the disciplined nature of Marxist political thought and leaves it arbitrary and ineffective. Rosa Luxemburg and the Spartacist League, which had attempted to overturn capitalism during the 1919 German Revolution, would become main targets of Lenin's attacks after World War I.
Spontaneism, however, remained a popular theory in opposition to the Third International's democratic centralism, and influenced the autonomist movement in the 1970s. Its influences can be felt in some parts of today's alter-globalization movement.