If protégé is the person who receives, so-to-speak, who is the giver? That is, what's the terms used for the person under whose patronage the protégé is?
The other person in the relationship with a protégé could be a protector, a patron or rarely a patrona (a female form of patron, normally not used, and hence implying that there is something significant in this protégé benefiting from a woman's patronage, hinting at a motivation for her generosity in the matter).
Most often though, the word is used to suggest that the protégé is learning from this person, and so that person is a mentor.
Certainly in the other direction, the person who benefits from a mentor is a protégé. (Unless again, we felt the need to distinguish a female protégée for some reason).
The patron is the person in question:
a patron supports an protects a protégé usually to furthers his career.