ENThis essay scrutinizes how the notion of the common good was interpreted within two distinct urban communities of the Polish–Lithuanian Commonwealth, in Royal Prussia and the Grand Duchy of Lithuania. Karin Friedrich underscores that while the discourse surrounding the common good held significant weight in Polish–Lithuanian political and moral deliberations, urban culture was largely overlooked. This was primarily due to the prevalent belief in the moral inferiority associated with urban and commercial activities. Despite this, the essay presents two case studies demonstrating how the principle of the common good, or “bonum commune,” was actualized in the Commonwealth’s cities. The examples provided are Danzig (Royal Prussia) during the city’s dispute with King Stephen Báthory and Slutsk (Grand Duchy of Lithuania) during the period of Prince Bogusław Radziwiłł’s ownership. Friedrich demonstrates that the common good was tightly interwoven with self-interest in urban socio-political and economic life. These two values bolstered each other, creating a potential symbiosis between the common good and individual benefit. Attempts to secure the common good were not perceived as sacrifices but as pursuits of prosperity and overall well-being. Keywords Poland–Lithuania – common good – Danzig – Slutsk – Hugo Grotius – urban life. [From the publication]