William Douglas, 1st Earl of Douglas was a Scottish nobleman, peer, magnate, and head of the Black Douglas family. Under his leadership, the Black Douglases continued their climb to pre-eminence in Scottish politics begun under his uncle, Sir James the Good, as well as their military dominance of the south of Scotland.

There are currently two earldoms of Mar in the Peerage of Scotland, and the title has been created seven times. The first creation of the earldom is currently held by Margaret of Mar, 31st Countess of Mar, who is also clan chief of Clan Mar. The seventh creation is currently held by James Erskine, 14th Earl of Mar and 16th Earl of Kellie, who is also clan chief of Clan Erskine.