Otto I (23 November 912 – 7 May 973), known as Otto the Great (German: Otto der Große; Italian: Ottone il Grande) or Otto of Saxony (German: Otto von Sachsen; Italian: Ottone di Sassonia), was East Frankish (German) king from 936 and Holy Roman Emperor from 962 until his death in 973. He was the eldest son of Henry the Fowler and Matilda of Ringelheim.
Otto inherited the Duchy of Saxony and the kingship of the Germans upon his father's death in 936. He continued his father's work of unifying all German tribes into a single kingdom and greatly expanded the king's powers at the expense of the aristocracy. Through strategic marriages and personal appointments, Otto installed members of his family in the kingdom's most important duchies.