Alan I of Vannes (died 907), known as the Great, was count of Vannes and duke of Brittany, from 877 to his death. He became ruler of Brittany after the death of his brother Pasquitan and his rival in Brittany, Gurvand. His accession was disputed with Judicael of Rennes, son of Gurvand, whom he defeated in battle in 888. Alan was the second son of count Ridoredh of Vannes and had the following issue:

• Pasquitan II, count of Vannes (died ca. 903)
• Unnamed daughter, who married Malhuedoc, count of Poher, and was the mother of Alan II.

After his death, no Duke succeeded him in Brittany until 936.

See also: Dukes of Brittany family tree

Preceded by: Pasquitan or Gurvand

Duke of Brittany disputed with Judicael

Succeeded by: Alan II