Which Byzantine emperor recognized Charlemagne as an emperor in 812?

Michael I recognized Charlemagne as an emperor in 812. The agreement acknowledged Charlemagne with the Byzantine titles imperator and basileus, although it did not recognize him as “Emperor of the Romans.”

The recognition followed years of tension between the Frankish and Byzantine empires. Pope Leo III had crowned Charlemagne emperor in Rome in 800, but Constantinople disputed the legitimacy of a western emperor. The two powers also competed over Venice, Istria, and influence in the Adriatic.

Michael reopened negotiations after succeeding Nikephoros I, who had died during the Bulgarian campaign of 811. The settlement returned Venice and Istria to Byzantine control while allowing Charlemagne’s imperial status to be acknowledged. This was diplomatic recognition, not a submission to Frankish rule.

A common mix-up is confusing Michael I with Irene or Nikephoros I. Irene’s government had rejected Charlemagne’s imperial claim, while Nikephoros negotiated earlier but did not grant the 812 recognition. Michael’s reign was brief: he ruled from 811 to 813 before being overthrown by Leo V.