The marriage of Otto II, co-emperor of the Holy Roman Empire, to Theophanu, a Byzantine princess, took place in Rome under the auspices of Pope John XIII. This union was not merely a personal alliance but a strategic partnership that sought to bolster ties between the influential Christian realms of the East and the West. The ceremony, imbued with political significance, emphasized the connections between the Byzantine Empire and the Holy Roman Empire during a time when both powers were navigating the complexities of medieval Europe and their respective roles in Christendom.

Theophanu entered into this marriage with an impressive lineage, as the daughter of Byzantine Emperor Romanos II. Her arrival in the West was marked by hopes of creating a more unified Christian front against common adversaries, including Islamic and pagan forces threatening both empires. The crowning of Theophanu as empress by Pope John XIII during the marriage ceremony not only validated her position but also underscored the Pope's influence in legitimizing political alliances. This act signified the intertwining of religious approval with secular power, a recurring theme in medieval governance.

This marriage would ultimately impact the political landscape of Europe. Otto II and Theophanu had two children, ensuring the continuation of their union’s legacy and further entrenching ties between the Holy Roman and Byzantine Empires. Their offspring would carry forward the diplomatic intentions of their parents, aiming to enhance cooperation between the two powerful dynasties.