Although it appears surprising that gas is put back into the ground after expending so much time, effort and money on extracting it in the first place, underground gas storage (UGS) plays an important role in the management of the gas supply chain. UGS has been used effectively for nearly a century to balance the mismatch in gas supply and demand. Its use continues to grow and with the advent of gas market liberalization, additional uses of UGS have been introduced. In several countries some 20–30% of the annual gas consumption is supplied through the use of UGS. This paper provides an overview of the most common use of UGS, the current status of UGS in the world and the main characteristics of the various types of facility: such as gas fields, aquifers and salt caverns. Aspects related to the planning and performance of gas storage facilities are also discussed.