noun
Refers to a person who follows utilitarianism, the ethical theory that the best action is the one that maximizes utility.
彼は功利主義者として、最大多数の最大幸福を重視する。
As a utilitarian, he values the greatest happiness for the greatest number.
功利主義 is the philosophy of utilitarianism, while 功利主義者 refers to a person who adheres to that philosophy.
Compound of 功利 (こうり, 'utility') + 主義 (しゅぎ, '-ism') + 者 (しゃ, 'person'). The term is a direct translation of the English 'utilitarian'.