Aristotle’s Nicomachean Ethics establishes happiness not as pleasure, wealth, honour, or momentary satisfaction, but as the highest and most complete end of human life. His central concept is eudaimonia, commonly translated as happiness or flourishing, which designates the condition of living well through the excellent exercise of human capacities. Since every art, inquiry, and action aims at some good, Aristotle argues that there must be a supreme good sought for its own sake, and this good is happiness. Yet happiness cannot be reduced to passive possession; it consists in activity of the soul in accordance with virtue. The decisive case study is Aristotle’s analysis of the specifically human function: plants live and animals perceive, but human beings uniquely act according to reason. Therefore, the good life is realised when reason governs desire, choice, and conduct through stable virtues such as justice, courage, temperance, and practical wisdom. Aristotle also recognises that external goods—friends, political stability, material sufficiency, and good fortune—support happiness, although they do not constitute its essence. His ethics thus avoids both crude hedonism and abstract idealism: happiness is neither mere feeling nor detached contemplation alone, but a sustained form of rational excellence embodied in action. Ultimately, Aristotle presents ethics as a practical science whose aim is not simply to know the good, but to become capable of living it.