The U.S. public debt is the amount of money that the United States federal government (not the states or banks or corporations or individuals) owes.

The calculation of the debt is subject to political manipulation and creative accounting, but the accounting assumptions behind any specific set of numbers can be made clear. As these are often also political assumptions, they form an important role in debates on U.S. fiscal policy, the most important of which is the U.S. budget deficit. Any budget deficit must be made up for by deficit spending, which increases the debt. A budget surplus, by U.S. law, must be used to pay down the debt. So these cannot be discussed separately.

Government bonds are part of the national debt, as are loans from banks, and Treasury securities. The debt also includes unfunded liabilities like pension plan payments and, by some measures, Social Security. Bonds sold for infrastructure projects are also part of the national debt. Some economists, but not all, include sums related to bills the government must pay for goods and services it has contracted for in the current fiscal year.