Jean I the Red (in Breton Yann Iañ ar Ruz, in French Jean I le Roux) (1217 – October 8, 1286), known as Jean the Red due to the colour of his beard, was Duke of Brittany, from 1237 to his death. He was son of Duke Pierre I and Alix of Thouars, heiress of the duchy. In 1236 Jean married Princess Blanche, daughter of King Theobald I of Navarre.
Jean was nominal duke from 1221, date of his mother’s death, although his father ruled as regent until he reached adulthood.
He experienced a number of conflicts with the Bishop of Nantes and the Breton clergy. He joined Saint Louis in the eighth crusade (1270), and survived the plague that killed the king. He then returned to his duchy. In Brittany he issued an edict expelling Jews from the duchy and cancelling all debts to them.