Margaret of Mar (died c. 1391) was Countess of Mar, an ancient Earldom in Scotland, in her own right.
She was a daughter of Domhnall II of Mar and after the death of her childless brother Thomas became Countess of Mar. She had married William Douglas, 1st Earl of Douglas, who was succeeded by their son, James Douglas, 2nd Earl of Douglas and Earl of Mar and Garioch in right of his mother, and when he fell, leading the Scots at the battle of Otterburn.
She was succeeded by her daughter, Isabel, who became Countess of Mar, possessed the Lordship of the Garioch, and also became the Countesss of the unentailed lands of the House of Douglas.
| Preceded by Thomas |
Countess of Mar 1374–1391 |
Succeeded by Isabella |