Fiduciary
Fiduciary is a general legal term, mainly present in the expression fiduciary duty.
An individual having a fiduciary duty essentially acts in the best interest of someone else โ in most cases financially speaking. The individual charged with a fiduciary duty is simply a fiduciary. Correspondingly, the other person that benefits from that duty is a beneficiary.
Examples of fiduciaries are the executors of a Will and the trustees of Trust.