Reprint of the Special Issue 'Water Supply System Reliability, Resilience, Safety and Risk Modelling & Assessment, 3rd Edition' (Water, ISSN 2073-4441). This Reprint gathers peer-reviewed papers on reliability, resilience, safety and risk assessment in water supply systems and related water infrastructure. It reflects the growing role of artificial intelligence, machine learning, transfer learning, cybersecurity, leak detection, water-loss analysis, pipe-break consequence assessment, groundwater vulnerability, water treatment plant reliability, financial impacts of boil-water advisories and hydrochemical data interpretation. The collected studies combine analytical, modelling, data-driven and case-study approaches to support more resilient, safe, cyber-aware and sustainable planning and operation of water systems under technical, environmental and socio-economic pressures.