Unequal exchange is a concept used in Marxian economics to denote forms of exploitation which commercial trade of any type can involve, if objects of unequal value are being exchanged or traded. Normally people will not trade unless they gain from trade, but obviously some might gain vastly more from that trade than others. The concept was theorised by Raúl Prebisch and popularised by Arghiri Emmanuel. Historically, the occurrence of unequal exchange is as old as the history of trade, and it is not limited to the capitalist mode of production. The rise of merchant capitalism depended to a great extent on unequal exchange.

If unequal exchange occurs in trading, the effect is, that producers, investors and consumers incur either higher costs or lower incomes (or both) in the buying and selling of commodities than they would have, if the commodities had traded at their “real” or "true" value. In that case, they are disadvantaged in trading, and their market position is worsened, rather than strengthened. On the other side, the beneficiaries of the trade obtain a superprofit.