In economics, a market structure with one dominant buyer and many sellers is called a monopsony.
The buyer has purchasing power because sellers compete to reach that single major customer. In a labor market, for example, one large employer may be the principal buyer of workers’ services in a town or specialized industry. The employer can often offer a wage below the level that would prevail with many competing employers, although the exact result depends on labor supply and other conditions.
Monopsony is the buyer-side counterpart to monopoly, in which one seller serves many buyers. The terms are not interchangeable: monopoly concerns control of supply, while monopsony concerns control of demand. A market can also contain a few powerful buyers; that structure is called an oligopsony rather than a monopsony.
Labor-market monopsony is especially important in economics because policies such as minimum wages can sometimes raise both wages and employment when employers have substantial buyer power. This differs from the standard competitive-market model, where individual firms generally cannot influence the market wage.