Globally interconnected power grids are proposed as a future concept to facilitate decarbonisation of the electricity system by enabling the harnessing and sharing of vast amounts of renewable energy. Areas with the highest potential for renewable energy are often far away from current load centres, which can be integrated through long-distance transmission interconnection. The concept builds on the proven benefits of transmission interconnection in mitigating the variability of renewable electricity sources such as wind and solar by import and export of electricity between neighbouring regions, as well as on other known benefits of power system integration. This paper reviews existing global and regional initiatives in context of a sustainable future and presents the associated benefits and challenges of globally interconnected power grids and intercontinental interconnectors. We find that while the challenges and opportunities are clearly qualified, actual quantification of costs, benefits and environmental implications of the global grid concept remains in its infancy, imposing a significant gap in the literature.