John I the Red (in Breton Yann Iañ ar Ruz, in French Jean I le Roux) (c. 1217/18 – 8 October 1286), known as John the Red due to the color of his beard, is Duke of Brittany, from 1237 to his death.

He is the son of Duke Peter I, Duke of Brittany jure uxeris and Alix of Thouars, hereditary Duchess of Brittany.