This paper presents an updated review of the external corrosion and failure mechanisms of buried natural gas and oil pipelines. Various forms of external corrosion and failure mechanisms such as hydrogen-induced cracking (HIC), hydrogen embrittlement (HE), corrosion fatigue (CF), stress corrosion cracking (SCC) and microbiologically influenced corrosion (MIC) for oil and gas pipelines are thoroughly reviewed. The factors influencing external corrosion and possible forms of environment-assisted cracking (EAC) of pipeline steels in the soil are also reviewed and analyzed in depth. In addition, the existing monitoring tools for the external corrosion assessment and the models for corrosion prevention and prediction, failure occurrence, and remaining life of oil and gas pipelines, are analyzed. Moreover, the articles on external corrosion management, reliability-based models, risk-based models, and integrity assessment including machine learning and fuzzy logic approaches, are also reviewed. The conclusions and recommendations for future research in the prevention and prediction of external corrosion are presented at the end.