In economics, a monopsony is a market form in which only one buyer faces many sellers. It is an example of imperfect competition, similar to a monopoly, in which only one seller faces many buyers. As the only or majority purchaser of a good or service, the "monopsonist" may dictate terms to its suppliers in the same manner that a monopolist controls the market for its buyer.

A monopsony is a market condition where multiple sellers, [the majority of sellers in that market] all have to sell to the same individual buyer because that buyer is buying a significant portion of the entire market. This gives the buyer the advantage because the buyer can keep asking each seller to match or undercut the competing sellers prices, thus driving down the prices of the products in that market.

The term was first introduced by Joan Robinson in her influential book, The Economics of Imperfect Competition. Robinson credits classics scholar Bertrand Hallward at the University of Cambridge with coining the term.