Standing on the shoulders of Plato and his school in Academia outside Athens, academies and learned societies (in the following academies) have been created extensively in Europe. The oldest existing one, Accademia dela Crusca, founded in 1582, became the role model for a number of others oriented towards languages, and another one, Die Deutsche Akademie der Naturforscher Leopoldina (1652), considered the oldest academy of science, has many followers throughout Europe. The European population of academies thus constitutes a network of elite institutions, largely based on the selection of new members by those who already are members. As a result academies and their members live in symbiosis: academies elect distinguished members in order to raise its reputation, and members get reputation by being members. Academies thereby appear to have become important for science policy in general and the selection of experts for science policy decisions in particular. Against this backdrop, the chapter aims at demonstrating the role of academies in policy decisions. For this purpose the chapter will briefly summarize the development of academies over time. This exposition will be followed by an analysis of the characteristics of academies. It will point to the two important roles expressed in mission statements of academies: (1) international collaboration and (2) interaction with society. These roles are played both by individual members and the national academies themselves. However, like many other organizational fields, that of academies has seen the emergence of organizations that organize individual organizations, sometimes labelled meta-organizations. The development of these international organizations will be summarized in a subsequent section, followed by one dealing with the relationship between European academies and society. A final section will present conclusions and discuss their implications for European science policy.