Cboe Global Markets, Inc. is an American financial exchange operator. In the U.S., it owns the largest exchange for trading in options, where it has a 30% market share, and the third-largest exchange for trading in equities, where it has a 10% market share. It operates the largest stock exchange in Europe, where it has a 25% market share. It is headquartered in Chicago, where it maintains an open outcry trading floor.