Son of Emperor Henry I of Saxony, Otto was crowned king of Germany in Aachen in 936. After taming a dangerous princely uprising led by his brother Henry and the Duke of Franconia (939), he tore control of Lorraine to the Carolingian Ludwig IV. In order to better assure the bases of his power in Germany he distributed the most important duchies (Lorraine, Bavaria and Swabia) to members of his lineage. In 951 he went down to Italy where he defeated Berengario and had himself crowned in Pavia. Back in Germany, he had to counter the rebellion of his son Liudolfo (953).
With Otto began the Drang nach Osten (the push towards the east) political and not only economic-settlement of the Germans: hardly defeated the Hungarians in the battle of Lechfeld (955) the king went to Elba where he reported numerous victories on the autochthonous slave populations . In the meantime, leaning on the great secular and above all ecclesiastical lords (bishops and abbots of the empire), he consolidated his power in Germany. In 961 he descended again to Italy where he finally defeated and deposed Berengario d'Ivrea.
He then headed, as an ally, to Rome where, at the beginning of 962, he made himself crowned Western emperor. Remained in Italy, two years later he deposed Pope John XII, considered too favorable to Berengario II. In 967 he returned to Italy both to have his son Otto II crowned and in view of military actions against the Lombards and Byzantines of southern Italy. These actions, even though they did not achieve any success on the field, allowed him to negotiate his son's marriage with the Byzantine princess Theophan. In the course of his reign, Otto always endeavored to intensify his ties with all the leaders of the ecclesiastical apparatus, also developing their territorial power. Stable within itself, the Ottonian kingdom also managed to organize an effective defense of the eastern border against Slavs and Hungarians.