Conan I of Rennes (927 - June 27 992), was count of Rennes and duke of Brittany, from 990 to his death. He became ruler of Brittany after a period of civil and political unrest, through his father, Judicael Berenguer, count of Rennes and great-grandson of Duke of Brittany. He married Ermengarde of Anjou and had the following issue:

Judith (982-1017), married Richard II, Duke of Normandy Judicael, count of Porhoert (died 1037) Geoffrey of Brittany, his heir Conan died in battle and is buried in Mont St Michel Abbey.