Isabella MacDuff, Countess of Buchan (probably died 1313–14) was a significant figure in the Wars of Scottish Independence. She was the daughter of Donnchadh III, Earl of Fife, and Johanna de Clare, daughter of Gilbert de Clare, 6th Earl of Hertford. She was married to John Comyn, Earl of Buchan and thus was the Countess of Buchan. After Robert the Bruce killed John III Comyn, Lord of Badenoch at Greyfriars Kirk in Dumfries, the Earl of Buchan joined the English side in the Scottish Wars of Independence. Isabella took the contrary view.