San Buenaventura de Guadalquini or San Buenaventura de Boadalquivi was a Spanish mission located on St. Simon's Island, Georgia, United States from between 1597 and 1609 until 1684, when pirates burned the mission and its town. The mission moved to the north side of the St. Johns River near its mouth, in present day Duval County, Florida under the name of Santa Cruz de Guadalquini or Santa Cruz y San Buenaventura de Guadalquini for a few years before merging with the mission San Juan del Puerto.