Isabel Douglas, Countess of Mar (c. 1360 – 1408) was Countess of Mar. Isabel was the sister of the famous James 2nd Earl of Douglas and Earl of Mar, who died leading the Scots to victory at the Battle of Otterburn. He died without any legitimate children and his sister Isabel inherited most of his property, excluding only the Douglas lands which could only pass through the male line. After being confirmed as countess she then became the most sought after bride in the realm and soon was married to Sir Malcolm Drummond, brother-in-law of King Robert III. This marriage however failed to produce any children and the Countess soon became the focus of several plots to usurp her lands by scheming noblemen.