|Death||September 17, 1148|
Conan III, also known as Conan of Cornouaille and Conan the Fat (Breton: Konan III a Vreizh, and Konan Kerne; c. 1093–1096 – September 17, 1148) was duke of Brittany, from 1112 to his death. He was the son of Duke Alan IV and Ermengarde of Anjou.
Conan III allied himself with Stephen of England in Stephen's war against the dispossessed Empress Matilda.
He married Maud, an illegitimate daughter of King Henry I of England before 1113. Conan and Maud had three children that are known:
- Hoel (1116 - 1156) – disinherited from the Ducal crown; Count of Nantes;
- Bertha (1114 - 1155) – married Alan of Penthièvre; upon Alan's death in 1146, she returned to Brittany;
- Constance (1120 - 1148) – married Sir Geoffroy II, Sire de Mayenne, son of Juhel II, Seigneur de Mayenne.
On his death-bed in 1148, Conan III disinherited Hoel from succession to the Duchy, stating that he was illegitimate and no son of his. By this surprise move Bertha became his heiress and successor. However, Hoel was to retain the county of Nantes.