In economics, free entry is a condition in which firms can freely enter the market for an economic good by establishing production and beginning to sell the product. The assumption of free entry implies that if there are firms earning excessively high profits in a given industry, new firms that also seek a high profit are likely to start to produce or change into a production of the same good to join the market. In such a case there are no barriers preventing a start-up firm from competing. Where an opportunity of a profit arises we assume that there will also be firms entering the market for the certain good and compete for it. In most markets this condition is present only in the long run.
The assumption of free entry doesn't mean that a firm is simply able to set up a shop without any costs incurred. It is clear that the new entrant needs to gain the capital that they need for operating in the industry. Therefore, even with a free entry to a market the entrant still has to face the same cost structure as does an already existing firm.
Free entry is part of the perfect competition assumption that there are an unlimited number of buyers and sellers in a market. In conditions in which there is not a natural monopoly caused by unlimited economies of scale, free entry prevents any existing firm from maintaining a monopoly, which would restrict output and charge a higher price than a multi-firm market would.
Free entry is usually accompanied by free exit, under which condition firms that are incurring losses (such as would happen if there are too many firms producing the product so that each is producing too little to be at its minimum efficient scale) can readily leave the market. However, exiting a market may involve abandonment costs.