Assigned to the Ministerio de la Presidencia, the Centro de Investigaciones Sociológicas (CIS) is an independent entity established to study Spanish society, mainly through public opinion polls.

Its present name and organisation date back to 1977, although its predecessor, the Instituto de la Opinión Pública (IOP), was founded in 1963. Since its creation, the CIS has been a privileged witness to the huge transformations that have taken place in Spain and it has contributed, with over 1,600 opinion polls, to providing better insight into the social and political situation over the last quarter of a century.