Health Technology Assessments (HTAs) have become increasingly central to strategic resource allocation in modern health systems, providing a structured and evidence-based framework for evaluating the clinical, economic, and ethical value of medical technologies. This systematic review explores the evolving role of HTAs in shaping healthcare financing and policy decisions across diverse health system contexts. Drawing upon peer-reviewed literature, institutional reports, and global case studies, the review identifies how HTAs inform reimbursement, pricing, and priority-setting processes, and how they contribute to the optimization of health outcomes within budget-constrained environments. The paper critically examines methodological approaches used in HTAs, the influence of data quality and availability, and the ethical considerations inherent in balancing cost-effectiveness with equitable access to innovation. Furthermore, it highlights significant challenges, including variability in HTA adoption, stakeholder misalignment, and the limited use of real-world evidence. The review also outlines future directions, such as the integration of artificial intelligence, dynamic assessment frameworks, and global harmonization efforts aimed at enhancing the utility and impact of HTAs. Ultimately, this paper underscores the strategic importance of HTAs as tools for sustainable healthcare financing and offers actionable insights for policymakers, researchers, and practitioners.