Bayan I was the first khagan of the Avar Khaganate, between 562 and 602.
As the Göktürk Empire expanded westwards on the Eurasian Steppe during the 6th century, peoples such as the Avars (also known as the "Pseudo-Avars", Obri, Abaroi and Varchonites) and Bulgars migrated into Central Europe and the Balkans. Bayan I led the Avars, along with some Bulgars into Pannonia, where the khaganate was established from 568.
By 562, the Avars and Bulgars had reached the Lower Danube: it was most likely in that year that Bayan became their supreme Khagan, as his predecessor, the Kutrigur khan Zabergan had died.
As allies of the Byzantine Empire (ruled at time by by Justinian I), the Avars had obtained a grant of gold to crush other nomads — the Sabirs, Utigurs, Kutrigurs and Saragurs - in the lands later known as Ukraine, a task they accomplished to the emperor's satisfaction. Bayan's Avars now exacted the renewal of the alliance, increased pay and a land to live in.
Bayan had eyed the plain of Moesia, just south of the Lower Danube, what would become northern Bulgaria, as his promised land, but the Byzantines were adamant the Avars should not in any case cross the river. So Bayan and his horde in 563 rode around the northern Carpathians to Germany, where they were soundly stemmed along the river Elbe by the Frankish king Sigebert I of Austrasia. This defeat induced them to come back on their footsteps to the Lower Danube region. After vainly trying to force the Danubian border when the new Byzantine emperor Justin II denied them both entry and wage, the Avars renewed their ride to Thuringia. This time (566) they did defeat Sigebert, but had nonetheless to stop; in the meantime the Göktürks, in pursuit of their former subjects, remained a real danger.