Geoffrey I, Duke of Brittany, (b. 980)
Geoffrey I (c. 980 – 20 November 1008), also known as Geoffrey of Rennes and Geoffrey Berengar, was the eldest son of Duke Conan I of Brittany. He was Count of Rennes (ruler of the Romano-Frankish civitas of Rennes), by right of succession. In 992 he assumed the title of Duke of Brittany, which had long been an independent state, but he had little control over much of Lower Brittany.