Francis I (in Breton Fransez I, in French François I) (11 May 1414 – 17 July 1450), was Duke of Brittany, Count of Montfort and titular Earl of Richmond, from 29 August 1442 to his death.

Francis and Yolande had a son, Renaud, Count of Montfort.

[3] Francis' second marriage was to Isabel of Scotland,[1] daughter of James I, King of Scots and Joan Beaufort.

[4] She had been intended to marry his father John V, Duke of Brittany, with the marriage contract signed on 19 July 1441 and ratified on 29 September 1441, but he died before the wedding took place.

Once in Brittany, Isabella married instead with the widowed eldest son of her groom.