oligarch:

(plural: ‘oligarchs‘; pronunciation: the letter ‘g’ is said with a ‘g’ sound as in “gun” and the letters ‘ch’ are said with a ‘k’ sound as in “king” — for the right pronunciation of this word, please click here)

‘oligarchy’ = a system of government ruled by a small group or a group of families

a member of a small group of people, not necessarily wealthy, that rules/governs a state (country) — one of the oligarchy,

a Russian oligarch, lazing on the treated skin of a polar bear

e.g.

In the present usage, a Russian or any other European billionaire with political connections is called an oligarch.

Whenever the European oligarchs are under pressure from their rivals in governments or from their financial troubles, they just sail or fly to the USA, and there they are called American oligarchs.

Since the word oligarch came into use in public domain, wealthy people with political connection in the governments in countries other the European countries have been called oligarchs; for example, Chinese oligarchs, South African oligarchs, etc.

For an informative article that explains what an oligarchy and an oligarch are, please click here, for an article about an Armenian oligarch that shows us how we come across this word in our daily browsing, please click here and for a news article that reports the atrocities of the oligarchs in South Africa, please click here.