A group of securities issued at the same time by the same issuer that have differing characteristics such as risk, reward, maturity, and credit rating.

In structured finance, it refers to one of several related securitized bonds offered as part of the same collateralized debt obligation, where each bond is a slice of the deal's risk. Tranches are usually identified by letters, with AAA ("triple A") the most senior, least risky, and lowest return bond. AA and A ratings indicate less senior and riskier bonds. Junior, unsecured tranches may be rated BB. However, ratings can fluctuate after the debt is issued and even senior tranches could be rated below investment grade (less than BBB). The bond's indenture usually details the payment of the tranches in a section often referred to as the waterfall (because the moneys flow down).

In a loan agreement, a loan may consist of a number of tranches with separate drawdowns, interest rates, and repayment terms.