Margaret Stewart, Countess of Angus and Mar (died 1417) was Countess of Angus and Lady of Abernethy in her own right.^[1] Her father was Thomas Stewart, 2nd Earl of Angus.

She was married to Thomas, Earl of Mar with whom she had no children. After her husband's death in 1374, she began an extramarital affair with William Douglas, 1st Earl of Douglas, who was married to the Earl of Mar's sister. With the Earl of Douglas, she had two children, George Douglas, 1st Earl of Angus (c. 1380–1403) and Lady Margaret Douglas who in 1404 received the lands of Bonjedward from her half-sister, Lady Isabel Douglas. The countess secured a charter of her estates for her son, to whom, in 1389 the title was granted by King Robert II.^[2]

• Earl of Angus

• Balfour Paul, Sir James, Scots Peerage IX vols, Edinburgh 1904. [1]
• Fraser, Sir William, The Douglas Book IV vols. Edinburgh 1885. [2]
• The Records of the Parliaments of Scotland to 1707 [3], K.M. Brown et al. eds (St Andrews, 2007–2011).

• thepeerage.com page

v t e Mormaers or Earls of Angus
[Known] 10th-century mormaers	Dubacan Cuncar
[Known] Mormaers from the Angus and Umfraville line	Gille Brigte Adam Gille Críst Donnchadh Máel Coluim Matilda (with 1. John Comyn; 2. Gilbert de Umfraville) Gilbert de Umfraville Robert de Umfraville
Earls from the Stewart line	John Stewart Thomas Stewart Margaret Stewart (with Thomas, Earl of Mar)
Earls from the Douglas line	George Douglas, 1st Earl William Douglas, 2nd Earl James Douglas, 3rd Earl George Douglas, 4th Earl Archibald Douglas, 5th Earl Archibald Douglas, 6th Earl David Douglas, 7th Earl Archibald Douglas, 8th Earl William Douglas, 9th Earl William Douglas, 10th Earl William Douglas, 11th Earl
As a subsidiary title	William Douglas, 11th Earl of Angus and 1st Marquess of Douglas James Douglas, 2nd Marquess of Douglas (and James Douglas, Earl of Angus) Archibald Douglas, 1st Duke of Douglas Duke of Hamilton from 1761
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