Autonomous communities are divided into provinces, which served as their territorial building blocks. In turn, provinces are divided into municipalities. The existence of both the provinces and the municipalities is guaranteed and protected by the constitution, not necessarily by the Statutes of Autonomy themselves. Municipalities are granted autonomy to manage their internal affairs, and provinces are the territorial divisions designed to carry out the activities of the State.

The current provincial division structure is based—with minor changes—on the 1833 territorial division by Javier de Burgos, and in all, the Spanish territory is divided into 50 provinces. The communities of Asturias, Cantabria, La Rioja, the Balearic Islands, Madrid, Murcia and Navarre are the only communities that comprise a single province, which is coextensive with the community itself. In these cases, the administrative institutions of the province are replaced by the governmental institutions of the community.