Duke Geoffrey I of Brittany was a nobleman who ruled from 990 to 1008. He was the son of Duke Conan I of Brittany and Ermengarde of Anjou. Geoffrey's reign was marked by efforts to strengthen the duchy and maintain its independence from neighboring powers. Geoffrey I is also known for his marriage to Hawise of Brittany, which helped to solidify alliances within the region. His legacy continued through his children, including Duke Conan II of Brittany, who succeeded him. Geoffrey's contributions to the stability of Brittany were significant during a time of political fragmentation in medieval France.