Aristocracy is a form of government that places strength in the hands of a small, privileged ruling class, the aristocrats. The term derives from the Greek aristokratia, meaning 'rule of the best'.
At the time of the word's origins in ancient Greece, the Greeks conceived it as rule by the best qualified citizens—and often contrasted it favourably with monarchy, rule by an individual. The term was first used by such ancient Greeks as Aristotle and Plato, who used it to describe a system where only the best of the citizens, chosen through a careful process of selection, would become rulers, and hereditary rule would actually have been forbidden, unless the rulers' children performed best and were better endowed with the attributes that make a person fit to rule compared with every other citizen in the polity. Hereditary rule in this understanding is more related to Oligarchy, a corrupted form of Aristocracy where there is rule by a few, but not by the best. Plato, Socrates, Aristotle, Xenophon and the Spartans considered Aristocracy to be inherently better than the ideal form of rule by the many, but they also considered the corrupted form of Aristocracy to be worse than the corrupted form of Democracy. This belief was rooted in the assumption that the masses could only produce average policy, while the best of men could produce the best policy, if they were indeed the best of men.
Later Polybius in his analysis of the Roman Constitution used the concept of aristocracy to describe his conception of a republic as a mixed form of government, along with democracy and monarchy in their conception from then, as a system of checks and balances, where each element checks the excesses of the other.
In practice, aristocracy often leads to hereditary government, after which the hereditary monarch appoints officers as they see fit.
In modern times, aristocracy was usually seen as rule by a privileged group, the aristocratic class, and has since been contrasted with democracy.


The concept evolved in Ancient Greece, whereby a council of leading citizens was commonly empowered and contrasted with representative democracy, in which a council of citizens was appointed as the "senate" of a city state or other political unit. The Greeks did not like the concept of monarchy, and as their democratic system fell, aristocracy was upheld.
In the 1651 book Leviathan, Thomas Hobbes describes an aristocracy as a commonwealth in which the representative of the citizens is an assembly by part only. It is a system in which only a small part of the population represents the government; "certain men distinguished from the rest". Modern depictions of aristocracy tend to regard it not as the ancient Greek concept of rule by the best, but more as an oligarchy or plutocracy—rule by the few or the wealthy.
The concept of aristocracy per Plato, has an ideal state ruled by the philosopher king. Plato describes these "philosopher kings" as "those who love the sight of truth" and supports the idea with the analogy of a captain and his ship or a doctor and his medicine. According to him, sailing and health are not things that everyone is qualified to practice by nature. A large part of the Republic then addresses how the educational system should be set up to produce these philosopher kings.


In contrast to its original conceptual drawing in classical antiquity aristocracy has been associated in the modern era with its more general and degenerated form the oligarchy, specifically aristocracy class based oligarchy, like entitled nobility as in monarchies or aristocratic merchant republics. Its original classical understanding has been taken up by the modern concept of meritocracy.


Aristocracies dominated political and economic power for most of the medieval and modern periods almost everywhere in Europe, using their wealth, control of the best land, and control of their tenants to form a powerful political force. In the 19th century the rising middle class produced rich businessmen, many of whom use their money to buy into the aristocracy. However, after the 1830s, in country after country, the aristocracies tended to lose their historic dominance over wealth and political power. The French Revolution in the 1790s forced many aristocrats into exile, relieving them of their lands and power. After the defeat of Napoleon in 1814, however, the exiles returned but they never recovered all their lands and never wielded as much political power. Beginning with Britain, Belgium, and Germany, industrialization in the 19th century brought urbanization, with the wealth increasingly concentrated in the cities, which increasingly took political power. Before 1789, aristocracies were typically closely associated with the church, especially the Catholic Church, but in the 19th century wave after wave of attacks on the Catholics weakened that element of the aristocratic coalition. As late as 1900, aristocrats maintained political dominance in Britain, Germany, Austria and Russia, but it was more precarious. World War I had the effect of dramatically reducing the power of the aristocrats in all major countries. In Russia they were expelled by the Communists. After 1900, Liberal and socialist governments levied heavy taxes on landowners, spelling their loss of economic power.