Alan III of Rennes was Count of Rennes and duke of Brittany, by right of succession from 1008 to his death.
Background
He was the son of Duke Geoffrey I and Hawise of Normandy. Alan succeeded his father as Duke of Brittany in 1008. Because he was still a minor at his father"s death, his mother acted as regent of Brittany while her brother Richard II, Duke of Normandy assumed guardianship over Brittany.
In 1018 Alan married Bertha of Blois, daughter of Odo II, Count of Blois and his second wife Ermengarde of Auvergne.
Career
Alan apparently took advantage of the resulting turmoil to break free of Norman suzerainty. In the early 1030s Robert I successfully attacked Dol and Alan"s retaliatory raid on Avranches was repulsed causing continued raiding back and forth between them. Alan III also assisted Herbert I "Wake-Dog" in his wars with Avesgaud, Bishop of Le Mans and was with the count in his attack on Avesgaud"s castle at Louisiana Ferté-Bernard destroying the castle and causing Avesgaud to flee.
On 1 October 1040, while besieging a rebel castle near Vimoutiers in Normandy, Alan III suddenly died.
According to Orderic, he was poisoned by unnamed Normans. By Bertha of Blois, he had two children:
Conan II, (d 1066), succeeded his father.
Hawise of Brittany, who married Hoel of Cornouaille. After 14 May 1046 his widow Bertha married secondly Hugh IV, Count of Maine.