<p>There is a great deal of excitement and momentum around hydrogen and green gases as clean energy sources because of the worldwide shift to net-zero energy systems. Pipelines are seen as a vital piece of infrastructure for transporting hydrogen and green gases safely, economically and at an amount and at a rate sufficient to allow these fuels to be used on a large scale; however, the introduction of these fuels into existing pipeline networks creates many new safety and integrity issues that must be managed. This article reviews some of the major challenges and opportunities associated with the creation of hydrogen and green gas pipeline systems, including issues related to hydrogen embrittlement, material degradation, gas leakage, gas quality and compatibility with existing infrastructure. Quantitative data show that hydrogen can significantly reduce the fracture toughness of metals exposed to it (up to 70% reduction in fracture toughness) and increase the rate at which cracks propagate (increased rate of crack growth by one order of magnitude) and increase the risk that gas will leak out of pipelines in comparison with natural gas pipeline systems. In addition, advanced analytical techniques reliant on probabilistic modelling, fracture mechanics, and real-time monitoring technologies are being used in the development of comprehensive risk assessments and integrity management systems. Mitigation measures, including derating of pipeline operating pressures, enhanced methods of inspecting pipelines, and the use of hydrogen-compatible materials, are also discussed. Also discussed is the potential for using digital technologies, including artificial intelligence (AI)-driven monitoring systems and digital twins, to increase safety within hydrogen and green gas pipeline systems. Finally, in addition to establishing a link between the safety of pipeline systems and the Sustainable Development Goals (SDGs), the review identifies several critical areas of research that need to be investigated in the future.</p>