Isabella MacDuff, Countess of Buchan (probably died c. 1314), 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 The 6th Earl of Hertford. She was married to John Comyn, 3rd 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. Mary Bruce was treated in a similar fashion at Roxburgh Castle.