Despite the omnipresence of the fiduciary in business organisations, there is an omission of theorisations of this legal concept within business ethics literature. This is surprising considering its widespread and embedded use, but even more so given that the presence of ethics within the fiduciary is increasingly contested ground. This article addresses both issues by theorising the fiduciary using an ontological analysis—one which subsequently helps identify a suitable ethical framework. The article argues on two grounds that the ontology of the (...) fiduciary is inherently relational; it renders the fiduciary’s implicit ontology explicit. Firstly, the fiduciary is shown to be process-oriented, indicating an open, emergent, and relational ontology at work. Secondly, historical investigation of the development of the fiduciary highlights its core relationship structure, and the interdependency and power dynamic embedded in the fiduciary are revealed. The argument is advanced that by bringing this inherent relational ontology to the fore, we can see how a relational ethical framework—the Ethics of Care—is best placed to explicate the ethics at work in the fiduciary. The article concludes with a discussion outlining how this ontological theorisation offers utility in steering future practice of the fiduciary. (shrink)