This paper is to examine what implications the regionalism in Spain has for its national development during the last two centuries. Since the beginning of the nineteenth century the regionalism (including territorial nationalisms in periphery) has played a central role in the history of Spanish state-formation. On the one hand, a strong regional identity was related to a structural weakness affecting Spanish nation-building and accused of forging the separatist national movements in the Basque, Catatonia Galicia and so on. On the other hand, the regionalism has contributed to enforcing the Spanish national consciousness in complex and contradictory ways. Therefore, on the contrary to our common understandings of regionalism, the Spanish regionalism has both enforced and counteracted the Spanish nationalism. In the late 1970s after the collapse of Franco regime, the long history of the Spanish regionalism resulted in a state system based on the regional political decentralization.