Abstract: The article considers the main principle of work of local governments in Spain – the autonomy principle formalized in the 1978 Constitution. The autonomy principle, whose concept has been developing by the theory of law and the law enforcement practice for almost 40 years, has significant impact on the character of interrelations of local authorities with public and regional authorities. Since interaction of local authorities and public and regional authorities is one of the key issues of local self-government, it seems necessary to define the key elements of the local autonomy principle, its characteristics and peculiarities. The author attempts at defining the idea of the local autonomy principle on the base of the analysis of statutory instruments, first of all, the provisions of the Constitution of Spain, the legal positions of the Constitutional Court of Spain, and the legal doctrine. Local self-government of Spain hasn’t been studied sufficiently enough in Russia. Taking into account the fact that Spain had started the formation of a new local self-government system, as did Russia a few years later, its experience in this sphere could be very important for the development of local self-government in Russia. Since the work of local authorities in Spain is based on the autonomy principle, the study of its concept could be important for the development of the science of local law, and the legislation on local self-government.