The fundamental element of sustainability in the health system is the financial sustainability that is at the heart of the health policy debate. Factors such as the aging of the world population, the emergence of new technological developments, increasing expectation and demand from the health system, increasing access to health services, and seeking quality health care services have begun to create significant pressures on health systems and threaten the financial sustainability of health systems. Sustainability and financial sustainability are very important concepts in evaluating countries’ health systems. However, there are no consensus definitions on these concepts in the literature. The aim of this study is to give information about the concepts of sustainability and financial sustainability, which have become an important topic of discussion in the health systems of the world countries in recent years, and to evaluate these concepts in terms of the health system.