Jean I, Duke of Alençon

John I of Alençon, called the Sage (1385 – 25 October 1415), was a French nobleman, killed at the Battle of Agincourt.
John was born in Château d'Essay, the son of Peter II of Alençon and Marie de Chamaillard. In 1404, he succeeded his father as Count of Alençon and Perche. He was made Duke of Alençon in 1414.
He commanded the second division of the French army at the Battle of Agincourt. When the English broke through the first division, he led a countercharge. He is sometimes credited with killing Edward, Duke of York, wounding Humphrey, Duke of Gloucester, and cutting an ornament from the crown of Henry V of England; but he was then overpowered by the King's bodyguard, and slain by the Welsh nobleman Dafydd Gam before he could yield himself.

In 1396, he married Marie of Brittany (1391–1446), daughter of John IV, Duke of Brittany. They had five children:

1. Pierre d'Alençon (1407, Argentan – 1408)
2. Jean d'Alençon, Duke of Alençon (1409–1476)
3. Marie d'Alençon (1410, Argentan, – 1412, Argentan)
4. Jeanne d'Alençon (1412, Argentan – 1420)
5. Charlotte d'Alençon (1413, Argentan – 1435, Lamballe)

He also had two illegitimate children:

1. Pierre d'Alençon (d. 1424, Battle of Verneuil), Lord of Gallandon
2. Marguerite d'Alençon, married Jean de St-Aubin, Lord of Preaux