Sort of-- a dollar bill is an "IOU Nothing". Still an IOU as pointed out by the other comments, but in practice it's more like a promise of the Federal Reserve to empty it's chest of assets (mostly dollar-denominated debt instruments) to give your dollar bill value.
Pre-1971 it was a claim on a defined amount of precious metals. Historically, precious metals and specifically gold were the sole non-debt currency, because it's a dense store of value whose custody you don't necessarily have to entrust to a 3d person.
Pre-1971 it was a claim on a defined amount of precious metals. Historically, precious metals and specifically gold were the sole non-debt currency, because it's a dense store of value whose custody you don't necessarily have to entrust to a 3d person.