A country's gross government debt (also called public debt or sovereign debt) is the financial liabilities of the government sector. Changes in government debt over time reflect primarily borrowing due to past government deficits. A deficit occurs when a government's expenditures exceed revenues. Government debt may be owed to domestic residents, as well as to foreign residents. If owed to foreign residents, that quantity is included in the country's external debt.

In 2020, the value of government debt worldwide was US$87.4 trillion, or 99% measured as a share of gross domestic product (GDP). Government debt accounted for almost 40% of all debt (which includes corporate and household debt), the highest share since the 1960s. The rise in government debt since 2007 is largely attributable to stimulus measures during the Great Recession, and the COVID-19 recession.

Governments may take on debt when the government's spending desires do not match government revenue flows. Taking debt can allow governments to conduct fiscal policy more effectively, avoid tax increases, and making investments with long-term returns. The ability of government to issue debt has been central to state formation and to state building. Public debt has been linked to the rise of democracy, private financial markets, and modern economic growth.

Actors that issue sovereign credit include private investors, commercial banks, multilateral development banks (such as the World Bank) and other governments. Low-income, highly indebted states tend to attain loans from multilateral development banks and other governments because they are considered too risky for private investors. Higher-income states tend to issue sovereign bonds, which are subsequently traded by investors in secondary markets. Ratings agencies (e.g. Moody's, Standard & Poor's) issue ratings that measure the credit-worthiness of governments, which may in turn affect the value of sovereign bonds in secondary markets.

Government debt is typically measured as the gross debt of the general government sector that is in the form of liabilities that are debt instruments. A debt instrument is a financial claim that requires payment of interest and/or principal by the debtor to the creditor in the future. Examples include debt securities (such as bonds and bills), loans, and government employee pension obligations.

International comparisons usually focus on general government debt because the level of government responsible for programs (for example, health care) differs across countries and the general government comprises central, state, provincial, regional, local governments, and social security funds. The debt of public corporations (such as post offices that provide goods or services on a market basis) is not included in general government debt, following the International Monetary Fund's Government Finance Statistics Manual 2014 (GFSM), which describes recommended methodologies for compiling debt statistics to ensure international comparability.

The gross debt of the general government sector is the total liabilities that are debt instruments. An alternative debt measure is net debt, which is gross debt minus financial assets in the form of debt instruments. Net debt estimates are not always available since some government assets may be difficult to value, such as loans made at concessional rates.

Debt can be measured at market value or nominal value. As a general rule, the GFSM says debt should be valued at market value, the value at which the asset could be exchanged for cash. However, the nominal value is useful for a debt-issuing government, as it is the amount that the debtor owes to the creditor. If market and nominal values are not available, face value (the undiscounted amount of principal to be repaid at maturity) is used.