Abstract: Widespread use of green hydrogen is a critical route to achieving a carbon-neutral society, but it cannot be accomplished without extensive hydrogen distribution. Hydrogen pipelines are the most energy-efficient approach to transporting hydrogen in areas with high, long-term demand for hydrogen. A well-known fact is that the properties of hydrogen differ from those of natural gas, which leads to significant variations in the pipeline transportation process. In addition, hydrogen can degrade the mechanical properties of steels, thereby affecting pipeline integrity. This situation has led to two inevitable key challenges in the current development of hydrogen-pipeline technology: economic viability and safety. On the basis of a review of the current state of hydrogen pipelines in terms of material compatibility with hydrogen, design methods, process operations, safety monitoring, and standards, this paper focuses on the following knowledge gaps in gaseous hydrogen pipelines: utilisation of high-strength materials for hydrogen pipelines, design of high-quality hydrogen pipelines, determination of hydrogen velocity, and repurposing of existing natural-gas pipelines. This review aims to identify the challenges in current hydrogen pipelines development and provide valuable suggestions for future research.