This article analyzes Da Nang’s marine economy as a process of spatial restructuring of the Han River estuary–Da Nang Bay area under the combined impacts of natural conditions and institutional transformations. The study draws upon archaeological evidence, administrative records, and maritime accounts. The analysis is structured into four coherent historical phases: (1) the prehistoric–ancient period, marked by the formation of marine livelihoods and river–sea exchange networks; (2) the eleventh to eighteenth centuries, characterized by Da Nang’s repositioning within the Central Vietnam port network through a “fore-port–central hub” model associated with Hoi An; (3) the nineteenth century to 1945, involving the modernization of the port city and its integration into the colonial economic system; and (4) the period from 1945 to the present, featuring reconstruction, renovation, and diversification of the marine economy (ports and logistics, fisheries, and marine tourism) under the imperatives of sustainability. The findings highlight Da Nang’s role as a strategic maritime “nodal point” and offer policy implications for dual-use and risk-adaptive marine governance.