Gero I, also known as Gero the Great, was a prominent German noble from the Duchy of Saxony during the reign of King and later Emperor Otto I (936–973). He held several high-ranking offices within the East Francia realm, most notably serving as a king's representative, or legate, in the Saxon duchy.
Gero was appointed as a margrave, a rank that placed him above other counts. Historically, he is recognized for his frequent involvement in German expansion into the lands of the Polabian Slavs, located east of Saxon and Thuringian territories. Due to this role, traditional historiography refers to him as the Margrave of the East and identifies the frontier province as the March of Gero.
Modern scholarly analysis has introduced nuance to these historical accounts. Some researchers question or reject traditional views regarding the scope of Gero's jurisdiction because several charters containing data on his march are now considered potential later forgeries.