AbstractThe Upper Silesian Coal Convention – a «family affair»?This article presents new evidence on the Upper Silesian Coal Convention, a coal-mining cartel in Upper Silesia, in existence from 1898 to 1925. The cartel had evolved from collusive agreements dating back to 1890 and accounted for approximately one fourth of Germany’s coal supply. Yet, market coverage and longevity of the convention, as well as the economic importance of the Upper Silesian industrial district in general, imply that this cartel has been understated in historical research so far. Aristocratic industrialists, the leading group of entrepreneurs in Upper Silesia, shaped the formation and operation of the cartel. They induced an oligopolistic market structure and social homogeneity among cartel members that facilitated cartel formation in Upper Silesia.