Isabel Marshal was a medieval English countess. She was the wife of both Gilbert de Clare, 4th Earl of Hertford and 5th Earl of Gloucester and Richard, 1st Earl of Cornwall. With the former, she was a great grandmother of King Robert the Bruce of Scotland.

Richard was an English prince who was King of the Romans from 1257 until his death in 1272. He was the second son of John, King of England, and Isabella, Countess of Angoulême. Richard was nominal Count of Poitou from 1225 to 1243, and he also held the title Earl of Cornwall since 1225. He was one of the wealthiest men in Europe and joined the Barons' Crusade, where he achieved success as a negotiator for the release of prisoners and assisted with the building of the citadel in Ascalon.