Saudi Arabia’s Vision 2030 infrastructure transformation requires project quality management systems (PQMS) that do more than control defects at inspection points. Mega projects must deliver compliant assets while reducing rework, material waste, delay, environmental impact and handover risk. This review paper examines how continuous improvement and sustainability can be integrated into PQMS for mega infrastructure projects in Saudi Arabia. It positions quality management as a strategic governance function that links ISO 9001-based process control, risk-based quality planning, inspection and test plans, non-conformance management, supplier quality assurance, digital traceability, corrective and preventive action, and management review with sustainability objectives such as resource efficiency, waste reduction, lifecycle value and responsible procurement. The study adopts a structured narrative review of recent literature on quality management systems, sustainable construction, Lean construction, Quality 4.0, project governance and Saudi Vision 2030 infrastructure delivery. It proposes a sustainability-integrated PQMS framework and an implementation roadmap tailored to roads, airports, tunnels, bridges, utilities and high-profile giga-project environments. The paper argues that continuous improvement tools, including PDCA, root-cause analysis, Kaizen, Six Sigma, NCR trend analysis and lessons-learned loops, can convert quality records into sustainability outcomes when they are embedded in project governance and supported by measurable KPIs. The expected contribution is a practical model for client, PMC, consultant, contractor and supplier organisations seeking to align quality excellence with sustainable infrastructure delivery. The framework supports reduced NCR recurrence, lower rework, stronger compliance, better supplier performance, improved handover readiness and enhanced long-term asset value under Saudi Vision 2030.