The world has become increasingly metacoupled through flows of materials, energy, people, capital, and information within and across systems. Transboundary flows, connecting adjacent and distant systems, are deemed the most critical indicators for measuring the intensity of interactions among coupled human-natural systems. To advance metacoupling flow research and governance, we make the first attempt to develop a typology of transboundary flows using six flow attributes (i.e., type, magnitude, direction, distance, time, and mode). Furthermore, we synthesize a portfolio of quantitative and practical methods for characterizing transboundary flows. To effectively govern transboundary flows for global sustainability and resilience, we highlight the need to recognize the shared risks and goals embedded in the interlinkages, use system thinking, and enhance multilateral cooperation.