An over-the-counter (OTC) market is a decentralized market in which market participants trade stocks, commodities, currencies, or other instruments directly between two parties and without a central exchange or broker. Over-the-counter markets do not have physical locations; instead, trading is conducted electronically. This is very different from an auction market system.

In an OTC market, dealers act as market-makers by quoting prices at which they will buy and sell a security, currency, or other financial products. A trade can be executed between two participants in an OTC market without others being aware of the price at which the transaction was completed.