Transboundary aquifers are an increasingly important water resource around the world. The chapter gives a historic overview of the steps and progress achieved in terms of enhancing the recognition, assessment, mapping, and governance of these aquifers. The last two decades of pioneering work, including concrete experiences from joint management and governance of key transboundary aquifers around the world and the tabling of the UN International Law Commission Draft Articles on Transboundary Aquifers at the UN General Assembly, have been instrumental in bringing the issue of internationally shared aquifers on the political and scientific agenda as well as in building a competent community of practice. Future improvement of governance of these aquifers hinges on further awareness raising and capacity development at multiple levels, and critically, the finalisation of the status of the Draft Articles in a shape that becomes tractable with aquifer states, amenable to application in concrete cases taking into account issues of sovereignty, and also enabling the implementation of more integrated and conjunctive (surface water and aquifer) approaches.