According to Wilson, "She became the only consort to receive the title 'co-empress' (coimperatrix augusta), and it was envisaged she would succeed as sole ruler if Otto II died without a son.

"[2] According to the marriage certificate issued on 14 April 972 Theophanu is identified as the neptis (niece or granddaughter) of Emperor John I Tzimiskes (925–976, reigned 969–976) who was of Armenian and Byzantine Greek descent.

She was of distinguished noble heritage: the Vita Mahthildis identifies her as augusti de palatio and the Annales Magdeburgenses describe her as Grecam illustrem imperatoriae stirpi proximam, ingenio facundam.

The Saxon chronicler Bishop Thietmar of Merseburg writes that the Ottonian preference was for Anna Porphyrogenita, a daughter of late Emperor Romanos II.

His advisors believed that Theophanu's relation to the usurper John Tzimiskes would invalidate the marriage as a confirmation of Otto I as Holy Roman Emperor.

[8] He was persuaded to allow her to stay when it was pointed out that John Tzimiskes had wed Theodora, a member of the Macedonian dynasty and sister to Emperor Romanos II.

After the marriage negotiations completed, Theophanu and Otto II were married by Pope John XIII in April 972 and she was crowned as Holy Roman Empress the same day in Rome.

Theophanu accompanied her husband on all his journeys, and she is mentioned in approximately one quarter of the emperor's formal documents – evidence of her privileged position, influence and interest in affairs of the empire.

Upon the death of Emperor Otto II, Bishop Folcmar of Utrecht released his cousin, the Bavarian duke Henry the Quarrelsome from custody.

[18] Duke Henry allied with Archbishop Warin of Cologne and seized his nephew Otto III in spring 984, while Theophanu was still in Italy in the royal palace of Pavia.

In fact, many queens in the tenth century, on an account of male rulers dying early deaths, found themselves in power, creating an age of greater diversity.

Her power as queen, empress and regent was based on the basis of Saxon tradition (which assigned the women an equal role in the family), Byzantine influence (which presented a model of a female counterpart to the emperor) and her mother-in-law Adelaide's legacy.

[8] She welcomed ambassadors, declaring herself "imperator" or "imperatrix", as did her relative contemporaries Irene of Athens and Theodora; the starting date for her reign being 972, the year of her marriage to the late Otto II.

In the North, she made a treaty with King Eric the Victorious, which promoted an alliance against Slavic tribes as well as reinforced trade and cultural connections.

She carried out at least one (successful) military expedition herself, in 987, when she marched with an imperial army to assist the Prince-Bishop Notker of Liège against Odo I, Count of Blois.

Some see her as passive, reactive and conservative while the others see her as extremely future-oriented and energetic; still others like Jestice opine that current evidences are not enough to definitely conclude that Theophanu and the other prominent female Ottonian rulers were extraordinarily talented as individuals or not but it is clear that the Ottonian society (which basically treated women and men as equals, except in physical prowess) allowed women the chance to succeed.