Port migration can be defined as the shift of port infrastructure and/or maritime traffic from one location to one or multiple other locations within a given period of time. Such migration processes can involve new port or new terminal development near existing facilities (e.g., a new port area being developed on a greenfield site away from an existing older port area) or at medium and longer distance. In a number of cases, port migration can change the physical and spatial features of the port, e.g., a river port can become an estuary or coastal port, in case of downstream development. Modern ports typically developed away from the obsolete facilities near the urban core to less-urban locations with ample space, and a better nautical accessibility, as exemplified in the “Anyport” model of James Bird. In this chapter, we undertake an overview of port migration throughout the world from two perspectives, qualitative and quantitative. The qualitative perspective discusses existing models, drivers, and impediments of port migration, supported by concrete cases from around the world. The quantitative approach measures port migration patterns using urban population and vessel traffic data of about 4,000 places from the 1950s to the present. We analyze the changing share of “outer” versus “inner” traffic by cargo and location type, world region, and urban area, concluding with a typology of port migration trajectories throughout the world.