<p>Contaminant intrusion into water distribution systems (WDSs) poses a persistent threat to drinking water quality, public health, and infrastructure resilience. Events such as negative pressure episodes, hydraulic transients, and intermittent water supply (IWS) conditions can allow microbial and chemical contaminants to enter pipelines through leaks, cracks, or defective joints. While several review articles have examined aspects of this issue, their coverage has remained fragmented, focusing narrowly on hydraulics, epidemiology, or regulation, and overlooking recent advances in digital monitoring and risk-based management. This study provides the first decade-long (2014–2024) systematic synthesis of experimental, analytical, numerical, and field-based research on contaminant intrusion. A structured literature search identified 31 relevant studies from major databases, screened according to PRISMA guidelines. Comparative evaluation highlights the strengths and limitations of existing experimental platforms, numerical simulations, and analytical models, emphasizing the influence of leak geometry, soil–pipe interactions, and transient pressure dynamics. Although only one study systematically combined Quantitative Microbial Risk Assessment <b>(</b>QMRA) with hydraulic modeling, its findings revealed that health risks from contaminant intrusion can exceed acceptable thresholds, underscoring the importance of integrating exposure assessment in future work. Importantly, this review identifies persistent gaps—including the limited integration of digital twins, artificial intelligence, and data-driven monitoring—and develops a prioritized future research agenda. By bridging engineering, environmental, and operational perspectives, the review establishes a forward-looking framework that supports utilities, regulators, and policymakers in advancing the safety, resilience, and sustainability of WDSs.</p>