In this article, I examine patterns of collective action in the South of Italy, a region where commons scholarship presents several challenges, mainly due to its feudal heritage. In analysing the history of Southern Italian commons, Elinor Ostrom's theories on polycentric governance are adopted. I propose a case study on the mountains of Sila, where collective action was institutionalised through a municipal organisation known as universitas casalium, consisting of the city of Cosenza and its hamlets. This institution collaborated with the royal government, creating a polycentric governance system where institutional functions contentiously intermingled, generating conflicting relations, but also unique governmental arrangements. Yet how did previous historical interpretations miss this point? Documentary evidence provides a clear answer: while the institutional recognition of the universitas casalium can be traced back as far as the twelfth century, a series of institutional reforms initiated in the mid-fifteenth century led to the progressive decline of the local institution and accordingly of the commons economy related to it. This loss of legitimacy derived from the emergence of feudal barons and later of landowners from the middle class, leading to the progressive dissolution of collective action in Sila as Italy moved towards Italian unification in 1861.