The oil market is undergoing fundamental change. New technologies are increasing the supply of oil from old and new sources, while rising concerns over the environment are seeing the world gradually moving away from oil. This spells a significant challenge for oil-exporting countries, including those of the Gulf Cooperation Council (GCC) who account for a fifth of the world’s oil production. The GCC countries have recognized the need to reduce their reliance on oil and are all implementing reforms to diversify their economies as well as fiscal and external revenues. Nevertheless, as global oil demand is expected to peak in the next two decades, the associated fiscal imperative could be both larger and more urgent than implied by the GCC countries’ existing plans.