Hydrogen has emerged as a promising alternative to meet the growing demand for sustainable and renewable energy sources. Underground hydrogen storage (UHS) in depleted gas reservoirs holds significant potential for large-scale energy storage and the seamless integration of intermittent renewable energy sources, due to its capacity to address challenges associated with the intermittent nature of renewable energy sources, ensuring a steady and reliable energy supply. Leveraging the existing infrastructure and well-characterized geological formations, depleted gas reservoirs offer an attractive option for large-scale hydrogen storage implementation. However, significant knowledge gaps regarding storage performance hinder the commercialization of UHS operation. Hydrogen deliverability, hydrogen trapping, and the equation of state are key areas with limited understanding. This literature review critically analyzes and synthesizes existing research on hydrogen storage performance during underground storage in depleted gas reservoirs; it then provides a high-level risk assessment and an overview of the techno-economics of UHS. The significance of this review lies in its consolidation of current knowledge, highlighting unresolved issues and proposing areas for future research. Addressing these gaps will advance hydrogen-based energy systems and support the transition to a sustainable energy landscape. Facilitating efficient and safe deployment of UHS in depleted gas reservoirs will assist in unlocking hydrogen’s full potential as a clean and renewable energy carrier. In addition, this review aids policymakers and the scientific community in making informed decisions regarding hydrogen storage technologies.