The potential for climate change induced by the continued use of fossil fuels which upon combustion produce the greenhouse gas, carbon dioxide is of increasing global concern. Hydrogen is an efficient and recyclable fuel that can be produced from water and offers great potential as an alternative fuel. However, the major obstacle to the utility of hydrogen as a fuel is its storage, particularly if it is to be used in the transport sector. Hydrogen can be stored in high-pressure containers, in liquid form, and absorbed as a hydride in hydride-forming metals, metallic glasses, or intermetallic compounds. However, high-pressure storage requires heavy and bulky vessels, while liquefied hydrogen storage is a safety risk and requires a substantial amount of energy to liquefy and maintain hydrogen in a liquefied state. While metals, metallic glasses, and intermetallic compounds can reversibly absorb a considerable amount of hydrogen under ambient conditions of pressure and temperature, desorption occurs at elevated temperatures. A disadvantage of metal hydrides is their weight and high operating pressures and temperatures. As an alternative, alanates such as LiAlH4 and NaAlH4 are also being investigated, but reversibility is an issue. Here we show that hydrogen storage in a crystalline clathrate hydrate can be easily achieved under mild conditions using tetrahydrofuran as a promoter molecule. This presents a very promising, innovative and alternative technology for the storage of sustainable hydrogen.