Wu Zetian (624 – 705), given name Zhao, was known posthumously as the Grand Sage Empress Zetian, hence the name Wu Zetian. Her ancestral home was Wenshui in Bingzhou (present-day Wenshui County, Shanxi Province). She was born in Chang'an, the Tang capital (some records say Guangyuan, Sichuan Province).

Her father Wu Shihuo was originally a timber merchant. He later joined the uprising led by Li Yuan, the Sui Dynasty’s military governor of Taiyuan. In the early Tang Dynasty, he rose to Minister of Works and Military Governor of Lizhou. Her mother Lady Yang was the daughter of Yang Da, a prime minister of the Sui Dynasty.

Legend has it that Wu Zetian showed extraordinary features even in her childhood. Yuan Tiangang, a renowned imperial physiognomist, once attended a banquet at the Wu family’s residence. During the feast, Wu Shihuo asked Yuan to read the faces of his family members. After observing Lady Yang, Yuan Tiangang said: "Madam has an extraordinary physiognomy; you will surely give birth to a noble son." He then looked at her two elder sons Wu Yuanqing and Wu Yuanshuang and remarked: "These two will reach the official rank of the third grade, yet they will not enjoy lifelong prosperity."

At that moment, a nanny carried in the young Wu Zetian, who was dressed in boys’ clothing. Yuan Tiangang studied the child closely and said: "This young lad has an unusual and spirited look. Let him walk a few steps." The nanny set the child down. After she took a few steps and lifted her head, Yuan Tiangang was greatly shocked: "This child has the eyes of a dragon and the neck of a phoenix, bearing the physiognomy of an ancient sage. She will attain supreme nobility and power!"

He examined her from the side again, filled with amazement and regret: "What a pity she is a girl. If this were a boy, he would surely become the ruler of the whole realm."