A philanthropist is someone who gives a lot of money to charitable causes, with a connotation of noble motives. A humanitarian is someone who acts on their strong desire to help their fellow humans, with a connotation of successfully helping many people. These have a broad area of overlap, but a person can be one without being the other.

One can be a philanthropist without being a humanitarian by, for example, donating large amounts of money to creating wildlife refuges. Charitable giving, but not to humans.

From the other direction, people like Norman Borlaug who devote their careers to helping other people are excellent examples of people who are humanitarians without necessarily being philanthropists.