Peter I of Brittany

Peter I of Brittany, called Peter Mauclerc (c. 1187–1250), was a younger son of Robert II of Dreux. In 1213 Philip II of France chose him as betrothed of Alix of Thouars, and Peter married the Duchess of Brittany in 1214. He ruled at her side and then served as regent for his son John I until 1237, and as Earl of Richmond from 1218 he led the barons opposing Blanche of Castile before submitting in 1234.

He joined the Barons' Crusade in 1239 and Louis IX's Seventh Crusade in 1249. Wounded and captured at Mansourah in 1250, he died at sea returning home and was buried at Braine.