A synthetic collateralized debt obligation, or synthetic CDO, is a transaction that transfers the credit risk on a reference portfolio of assets. The reference portfolio in a synthetic CDO is made up of credit default swaps. Thus, a synthetic CDO is classified as a credit derivative.

While the underlying assets of regular CDOs are traditional fixed-income assets, such as loans, mortgages, and bonds, synthetic CDOs use non-cash assets as the underlying asset, such as credit default swaps, options, and other such contracts. Synthetic CDOs typically offer higher yields than traditional CDOs.

Credit default swaps are also used to structure synthetic collateralized debt obligations (CDOs). Instead of owning bonds or loans, a synthetic CDO gets credit exposure to a portfolio of fixed income assets without owning those assets through the use of CDS. CDOs are viewed as complex and opaque financial instruments.

When the housing bubble burst and subprime borrowers went into default at high rates, the CDO market went into a meltdown. This caused many investment banks to either go bankrupt or be bailed out by the government. Despite this, CDOs are still in use by investment banks today.