Prosperity signifies success in economic performance. Economic performance always takes place in a spatial context. And institutions matter in economic performance. These three interwoven themes underlie this inquiry into the regional economy of southern Fukien province during the Sung and Yuan dynasties, when the area was one of the most prosperous regions in China. Through a meticulous reading of the sources, the author seeks to understand the meaning of prosperity in the premodern Chinese context and argues that we have to understand economic performance as a process occurring in space and influenced by institutions, which affect economic actors particularly through the means of transaction costs.