In sociology, the ruling class is a social class who set and decide the political agenda of society. Under capitalism, the ruling class is the capitalist class; the private owners of industry.
In the modern era of imperialism and capitalist globalization the ruling class is a network of transnational capitalists which do not have allegiance to any nation; their only allegiance is to their personal accumulation of wealth.
History
Historically, the ruling class has transitioned according to changes in the mode of production. Under feudalism, the ruling class was comprised of feudal lords, under slavery, the ruling class was the slaveowners, and so on.