With its vast oil reserves, Saudi Arabia has invested billions in expensive and energy-guzzling desalination technologies. In 1970, Saudi Arabia opened its first modern desalination plant in Jidda, designed by the U.S. Department of the Interior’s Office of Saline Water and built by a subsidiary of the Coca Cola Company. As the kingdom plotted its embrace of large-scale desalination, it rapidly became clear that the project would assume gigantic proportions. In 1974, a royal decree created an independent government body, the Saline Water Conversion Corporation, armed with broad powers to exploit desalination technology. Ever since the monarchy’s move to total reliance on desalination technology, this prototypical petro-state has transformed itself into a veritable “saltwater kingdom,” ushering in an era from which there could be no turning back. Oil and water have become completely interdependent. Not only have oil revenues subsidized water for the kingdom’s subjects; oil itself has become a necessary ingredient in water’s production. But water is no ordinary public handout produced by petro-state rentierism. Unlike the alchemy of turning oil into government revenue and private wealth, the production and consumption of desalinated water has created even more fundamental forms of material dependency. Through the magic of turning oil into water the Saudi state has arguably cast its most awe-inspiring and terrifying spell over its subjects. The kingdom’s embrace of multi-stage flash and reverse osmosis desalination technologies has been a key component in the Saudi state’s continued modernization and demographic explosion. This resource-intensive solution is predicated on the conceit that oil production and revenues will be able to perpetually keep up with the unbridled development that they have enabled. In order to map the development of desalination technology in Saudi Arabia, from the 1930s onward, but especially after World War II, I argue that Saudi reliance on American hydraulic expertise was a critical compliment to the development of the kingdom’s massive petroleum reserves. Indeed, American assistance in the development of the kingdom’s water was a fundamental element of American-Saudi relations. Thus, as the United States began to invest in experimental desalination techniques for domestic uses between the 1950s and 1970s, the transfer of these new technologies emerged as a lynchpin of American Cold War technocratic diplomacy in Saudi Arabia, Israel, and the wider Middle East. And in turn, large-scale desalination projects became central to Saudi monarchy’s visions of development and the environmental management of its subjects.