Conan III of Cornwall (1070-1148) was duke of Brittany, from 1112 to his death. He was son of Duke Alan IV and Ermengarde of Anjou. He married before 1113 to Maud, an illegitimate daughter of King Henry I of England. By her he had two daughters: Constance and Bertha of Brittany and duke Hoel III. On his deathbed he disinherited his only son, Hoel, for reason of illegitimacy.

See also: Dukes of Brittany family tree