Gero

thumb|right|200px|14th-century wall painting depicting Gero in the church he founded at Gernrode

Gero I ( 900 – 20 May 965), sometimes called the Great (), was a prominent German noble from the Duchy of Saxony in the East Francia, who held several offices during the reign of king and later emperor Otto I (936–973). As one of the most notable counts in northern regions of Otto's realm, Gero was appointed as king's representative (legate) in the Saxon duchy. He was also appointed as margrave (), thus ranking above other counts. The nature and scope of his jurisdiction as margrave was indicated in several sources, such as the Thietmar's Chronicle from the beginning of the 11th century, that mentions Gero as Margrave of the East (). Since various sources provide data on Gero's continuous and frequent involvement in German expansion towards the lands of Polabian Slavs, that lied to the east of Saxon and Thuringian lands, traditional historiography regarded Gero as margrave over the subdued Slavic regions, thus coining the term March of Gero (). Newer scholarly analyses have shown that some charters that contain data on Gero's march (frontier region) should be considered as later forgeries, thus leading modern researchers to question or reject various traditional views regarding the nature and effective scope of such a frontier province in the middle of the 10th century.