A trading order that has not been executed. This order remains in the system (books of a broker) until it is filled or cancelled by the trader or market participant who originally placed it. Usually, open orders are those that remain unfilled for more than one day because a condition set by the trader has not been met- e.g., a specific price level (as in a limit/ stop order).

An open order may also arise when an order is placed after a market’s working hours, leaving it unfilled due to non-existence of the market at the time.