The rule of a society or state by a smaller group within it.

The Greeks recognized it as a form of government. Most early Greek states were oligarchies, though the size of the group varied.

The feudal oligarchy in England was confined at first to those of Norman descent. It was a closed oligarchy but most oligarchies are adoptive, that is people can be invited to join, perhaps by education. The Church in Feudal times was adoptive, and a poor person could sometimes rise in the hierarchy.

Most modern states could be classified as oligarchies in one form or another. Thus South Africa during the Apartheid period was ruled by that group consisting of those recognized as being of European descent - thus closed (and within that group the Afrikaners were dominant, and within that group the Broederbond, a semi-secret society possibly made the policy); the Soviet Union was ruled by the Communist Party. Membership was to some extent open, but promotion was by those already with power. The Nomenklatura was the list of those eligible for appointments. In those states classified as democracies the oligarchy may be concealed by a form of election - that is, in practice the electors choose from among members of the implicit oligarchy (much better than having no choice at all). In Iran only those selected by the Mullas can be elected by the people.

The structure of the Catholic Church is similar to that of the former Communist Party of the Soviet Union. Officials are not elected by the ordinary members. The Pope is elected by the Cardinals who have been selected by a previous Pope. Thus it is an adoptive oligarchy, and self-perpetuating, with no popular input. In the past, however, the election was influenced by a group of Roman aristocratic families, and also by the Great Powers, such as the Holy Roman Emperor, the kings of France and Spain and others.

Is Britain an oligarchy? Many of those holding real power appear to have attended the small group of private schools and the two oldest English universities. (But in the past the grip of this group was much more complete). Candidates for election are chosen by the party activists or the party central offices. However, it is possible for people outside this group to gain office (e.g. Margaret Thatcher and her successor). Some believe there is a limit to what any party can achieve, set by the oligarchy. However, the truth may be that circumstances (e.g. the power of allies) may be the real limit. There are also the secret services which may behave like an inner oligarchy.

Is the United States an oligarchy? In theory it is a democracy with every post open to anyone. In practice those standing for election need large amounts of money for campaigning. Most candidates receive money which tends to come from the Corporations, whose interests and desires are therefore met by those elected with their money.

These wishes include low taxes for the corporations and their executives, and therefore a weak government, unable to regulate their activities, even if they are contrary to the needs of the voters.

Is this a recreation in modern conditions of feudalism?

Perhaps this is the reason fewer and fewer people vote, as all elected officials pay more attention to those who give them money than to the electors.

There is a loose use of the term oligarch to refer to the group of people who gained control of the Soviet Union's assets after the end of communism. Thus the hyper-rich to whom such assets as the oil industry were given are sometimes called the oligarchs. But they have little political power as the power of the state remains with the post KGB group.

Max Keiser on financial oligarchy