The Northern Zhou dynasty of China had nine empresses consort in its history (although the first two used the alternative title of "Heavenly Princess" (天王后, Tian Wanghou), five of whom were the wives of emperors:
Further, Emperor Xuan, after he had become retired emperor, created four of his concubines empresses as well, in contravention to the convention of having only the emperor's wife being empress[3]: