A type of treasury security that constitutes a short-term debt obligation in the form of a uniform security (fixed income security) issued and backed by a treasury department in a country. T-bills (treasury bills) have a a maturity of one year or less, i.e., usually for terms ranging from 4 to 52 weeks. Treasury bills (or simply, bills) are sold at a discount or at par (face value).

Given their short-term life cycle, treasury securities are considered money market instruments. For holders (investors), treasury bills are a secure, short-term investment, offering  returns on a relatively short commitment of funds (the securitized loan extended by the holders, collectively, to the issuer, i.e., issuing treasury department that acts on behalf of a government at large).