Geoffrey I, duke of Brittany (born 980)

Geoffrey I, also known as Geoffrey of Rennes and Geoffrey Berengar, was Duke of Brittany from 992 until his death, and also Count of Rennes by right of succession. The eldest son of Duke Conan I of Brittany, he assumed the title of Duke of Brittany upon his father's death in 992. Brittany had long been an independent state, but he had little control over much of Lower Brittany.