UST is the abbreviation for the United States Treasury, the federal government division that manages U.S. finances. UST is commonly used to reference debt that is issued by the United States.

Organizations under the purview of the UST include the IRS, U.S. Mint, the Bureau of Public Debt, the Office of the Comptroller of the Currency, and the Alcohol and Tobacco Tax Bureau.

UST securities are presumed to have little to no risk of default.