Fiduciary debt refers to a form of debt that originates from a fiduciary relationship, as opposed to a strictly contractual one.

In a fiduciary relationship, one party (the fiduciary) is entrusted with managing the assets or interests of another party. Fiduciary debt occurs when the fiduciary takes on debt on behalf of the other party.

The fiduciary is duty-bound to act in the best interests of the other party, with the debt incurred serving to benefit that party's assets or interests