Which theory states the ethical behaviour is that which best serves long-term self-interests

Ethical egoism is the theory that states ethical behavior is that which best serves long-term self-interests. This theory asserts that individuals should prioritize their own interests above all others and make decisions based on what will benefit themselves in the long run. Proponents of ethical egoism argue that acting in one's self-interest ultimately leads to the greatest overall happiness and well-being.