Oligarchy is a conceptual form of power structure in which power rests with a small number of people. These people may or may not be distinguished by one or several characteristics, such as nobility, fame, wealth, education, or corporate, religious, political, or military control.

The iron law of oligarchy is a political theory first developed by the German-born Italian sociologist Robert Michels in his 1911 book Political Parties. It asserts that rule by an elite, or oligarchy, is inevitable as an "iron law" within any democratic organization as part of the "tactical and technical necessities" of the organization.