This chapter defines the formation of maritime space in the High Qing. This entails a complex process of social construction, based on three interacting mechanisms: external utilization, internal perception, and regulatory representation. Hence, any in-depth analysis of the sea space not only requires an examination of its natural geography (as in Chapter 1) or its “deep structure,” but also entails an investigation into the history of how the sea was used and conceptualized. This chapter analyzes the high Qing emperors and their advisers’ nuanced conceptualizations of the maritime world. It will show that the distinction between an “inner” and an “outer” sea space that emerged in the high Qing framed many of the policies that were adopted during the reins of three consecutive emperors (Kangxi, Yongzheng, and Qianlong). To a substantial degree, the idea of an inner–outer binary formed the conceptual framework of Qing maritime policies; it is also the foundation of this study.