Conan I (died 27 June 992), nicknamed Le Tort (The Crooked), was the Duke of Brittany from 990 to his death.

Conan was the son of Judicael Berengar, succeeding his father as Count of Rennes in 970.

Conan assumed the title of Duke of Brittany in the spring of 990 following his attack on Nantes and the subsequent death of Count Alan.^[1] As Duke, his rule succeeded the Regency that governed Brittany during the life of Drogo and the fractured rule of Brittany after Drogo's death by his illegitimate brothers Hoël and Guerech, and the latter's son Alan.^[2] The fractured rule over Brittany resulted in a short vacancy in the title Duke of Brittany. Conan I had to ally himself with Odo I, Count of Blois in order to defeat Judicael Berengar before he could assume the title of Duke.^[3]

In a charter dated 28 July 990, Conan gave the lands of Villamée, Lillele and Passille to Mont Saint-Michel, all of which later became part of the seigneury of Fougères.^[4]

Conan married Ermengarde-Gerberga of Anjou,^[a][7] in 973, daughter of Geoffrey I, Count of Anjou and Adele of Vermandois.^[8] Conan's alliance with Odo of Blois ^[2] had helped him defeat Judicael Berengar.

The alliance with Blois eventually became troublesome and he later needed to "rid himself of influence from Blois, [which he accomplished by signing] a pact with Richard I of Normandy; [this pact] established firm Breton-Norman links for the first time."^[3] Richard I had married the daughter of Hugh I the Great, and after this marriage had re-asserted his father's claim as Overlord of the Breton duchy. ^[3] Conan I's pact with Normandy strengthened that assertion but the historical documentation for that Overlordship claim remains doubtful because it largely appears only in the less than authoritative writings of Dudo of Saint-Quentin.^[3][b]

Conan died fighting his brother-in-law Fulk Nerra, Count of Anjou at the Battle of Conquereuil on 27 June 992.^[10] Conan is buried at Mont Saint-Michel Abbey.^[11]

Conan and his wife Ermengarde-Gerberga had:

• Geoffrey (c. 980–1008), the eventual heir.^[12]
• Judith (982–1017), married Richard II, Duke of Normandy.^[12]
• Judicael, count of Porhoët (died 1037).
• Hernod.
• Catuallon, Abbot of Redon

• Counts of Rennes
• Dukes of Brittany
• Dukes of Brittany family tree

• Alexander, Jonathan James Graham (1970). Norman illumination at Mont St Michel, 966–1100. Oxford, UK: Clarendon Press.
• Bachrach, Bernard S. (1993). Fulk Nerra, the neo-Roman consul, 987-1040: A Political Biography of the Angevin Count. Berkeley and Los Angeles: University of California Press.
• Bachrach, Bernard S. (2002). Warfare and Military Organization in Pre-Crusade Europe. Ashgate Publishing.
• Delumeau, Jean (1969). Histoire de la Bretagne. Toulouse, France: Edouard Privat editeur; Jean Delumeau, directeur, with contributing authors P-R Giot, J L'Helgouach, J Briard, J-B Colbert de Beaulieu, L Pape, P Rache, G Devailly, H Touchard, J Meyer, A Mussat, and G Le Guen (chapters do not specify individual authors).
• Keats-Rohan, K.S.B. (1994). 'Two Studies in North French Prosopography', Journal of Medieval History Vol. 20.
• Glaber, Rodulfus (1989). France, John (ed.). The Five Books of the Histories. The Clarendon Press.
• Price, Neil S. (1989). "The Vikings in Brittany" (PDF). Saga-Book of the Viking Society. XXII (6): 319–440.