The article deals with the topic of the Third Mission (or Third Stream), i.e. the social and cultural stream of the university. In Italy academic and reseach libraries are strengthening their activities of Public Engagement by organizing manifold events. These activities essentially follow three drivers: the development and exploitation of the Cultural Heritage; the support to the Open Science paradigm; the Public Engagement, i.e. the participation in school projects, the collaboration in cultural locally-organized events, i.e. festivals, the European Researchers’ Night, Science cafés etc. By performing all these public activities, academic libraries play a concrete role in the development and the success of the Third Mission. Thus, the Third Mission offers the opportunity to rethink the traditional role of the academic library and to reflect on its social inclusive role.