1. (economics) a market in which control over the supply of a commodity is in the hands of a small number of producers and each one can influence prices and affect competitors

An oligopoly (from Greek ὀλίγος, oligos "few" and πωλεῖν, polein "to sell") is a market structure in which a market or industry is dominated by a small number of large sellers or producers. Oligopolies often result from the desire to maximize profits, leading to collusion between companies. This reduces competition, leading to higher prices for consumers and lower wages for employees.

Many industries have been cited as oligopolistic, including civil aviation, electricity providers, the telecommunications sector, Rail freight markets, food processing, funeral services, sugar refining, beer making, pulp and paper making, and automobile manufacturing.

Most countries have laws outlawing anti-competitive behavior. EU competition law prohibits anti-competitive practices such as price-fixing and manipulating market supply and trade among competitors. In the US, the United States Department of Justice Antitrust Division and the Federal Trade Commission are tasked with stopping collusion. However, corporations can evade legal consequences through tacit collusion, as collusion can only be proven through actual and direct communication between companies.

It is possible for oligopolies to develop without collusion and in the presence of fierce competition among market participants. This is a situation similar to perfect competition, where oligopolists have their own market structure. In this situation, each company in the oligopoly has a large share in the industry and plays a pivotal, unique role.