This chapter explores the link between sovereign debt and financial sustainability in central governments, clarifying sustainability mechanisms specific to the public sector. They refer to the connection between public debt and the monetary basis, as well as the general interest missions performed by the public sector to cover collective and long-term obligations and guarantees. By examining matters raised to this specificity, we offer an original position on the financial sustainability of central governments.In recent decades, there has been a trend toward convergence between the private and the public modes of accounting and finance, including related financial sustainability criteria. Financial sustainability of central governments was then allegedly aligned with that of business firms. Our approach argues that some financial mechanisms that lie at the heart of sustainability of public entities are specific and pertain to the public sector sphere. To illustrate this specificity, three issues are especially addressed: (i) the taxing power; (ii) the public debt management and its refinancing mechanism, and (iii) the collective engagement represented by pay-as-you-go pension obligations. A theoretical framework is then developed and corroborated by numerical illustration and case studies in practice and regulation. One case study concerns the sustainability measures adopted under “the Excessive Debt Procedure Criteria” by the European Union (EU), which may show inconsistency between management by financial indicators and sovereign sustainability.