A marketplace where transactions of selling new issues are carried out before an initial public offering (IPO) listing and over the period from the IPO start date to the allotment date. IPO grey market is the over-the-counter market (OTC market) where deals are executed only among a select or trusted group of investors, rather than the public.

Grey market IPO (or IPO grey market) is an unofficial market where market players (usually individuals) buy/ sell new issue securities before the official release date. It is an unofficial over-the-counter market, that is subject to no regulations. All transactions are carried out on a personal basis, and usually by direct means of payments (cash), where stock exchange or brokers are not involved in such transactions, either for execution or support.

Trading in such a market involves no official platform or rules of trading.