Fiduciary: A fiduciary is a person who holds a legal or ethical relationship of trust with one or more other parties. Typically, a fiduciary takes care of money or other assets for another person. A fiduciary duty is the legal responsibility to act solely in the best interest of another party. “Fiduciary” means trust, and a person with a fiduciary duty has a legal obligation to maintain that trust. Being a fiduciary thus requires being bound both legally and ethically to act in the other’s best interests.