Gender wage inequality remains one of the most persistent manifestations of labour market disparities worldwide. While human capital differences are frequently cited as the primary explanation, growing evidence suggests that wage gaps emerge from a broader interaction between individual endowments, labour market structures, and institutional constraints. This systematic literature review (SLR) examines the determinants of the gender wage gap from a human capital inequality perspective.The study identifies 1,267 publications across Scopus, Web of Science, and Google Scholar, from which 63 peer-reviewed articles were selected following a rigorous multi-stage screening process. Based on this synthesis, ten key determinants of the gender wage gap are classified into three analytical clusters: Human capital endowments, structural labour market mechanisms, institutional and cultural determinants. The findings demonstrate that gender wage inequality cannot be explained solely by observable productivity-related characteristics. Instead, wage disparities arise from the processes governing the formation, allocation, and pricing of human capital within labour market institutions. Institutional and structural factors significantly influence both the utilization of human capital and the returns paid for it. By integrating fragmented strands of literature into a coherent classification framework, this study provides a conceptual foundation for subsequent empirical modelling and evidence-based policy design aimed at reducing labour market inequality.