Geoffrey I (c. 980 – 20 November 1008), also known as Geoffrey of Rennes and Geoffrey Berengar, is Duke of Brittany from 992 until his death, and also Count of Rennes (ruler of the Romano-Frankish civitas of Rennes) by right of succession. The eldest son of Duke Conan I of Brittany, he assumei the title of Duke of Brittany upon his father's death in 992. Brittany has long been an independent state, but he has little control over much of Lower Brittany.