Alan III, Duke of Brittany
| Alan III | |
|---|---|
| Duke of Brittany | |
| Reign | 20 November 1008 – 1 October 1040 |
| Predecessor | Geoffrey I |
| Successor | Conan II |
| Regent | Hawise of Normandy (Regent 1008–1026) |
| Born | c. 997 |
| Died | 1 October 1040 Vimoutiers |
| Spouse | Bertha of Blois |
| Issue | Conan II, Duke of Brittany Hawise, Duchess of Brittany |
| House | Rennes |
| Father | Geoffrey I, Duke of Brittany |
| Mother | Hawise of Normandy |
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Alan III of Rennes (c. 997 – 1 October 1040) (French: Alain III de Bretagne) was Count of Rennes and duke of Brittany, by right of succession from 1008 to his death.