Towards the end of the twentieth century, polycentricity was introduced into China as a new planning concept. Subsequently, a number of mega city regions applied polycentric spatial planning strategies, designed to facilitate more sustainable and balanced development, by promoting expanded settlements or subcentres at the edge of the central cities. These urban clusters have often been termed edge cities in the West. Although edge urban areas in China bear some resemblance to Western edge cities, we argue that these growing centres need to be understood through the lens of a polycentric development framework specific to China. This article investigates the formation of edge urban areas as part of polycentric development practices, with particular reference to the specificities of the Chinese context. Guangzhou, a mega city region, is selected as the polycentric context within which the embedded edge urban area Nansha is located. After exploring Nansha’s spatial features, functional identities and governance arrangements, we suggest that the area has experienced a typical development trajectory associated with different dynamics at each stage of its growth. Nansha’s formation as an edge urban area is in line with the delivery of a polycentric spatial structure for the Guangzhou mega city region.