Mary Stewart, Countess of Arran (13 May 1453 – May 1488) was the elder daughter of James II of Scotland and Mary of Guelders. Her brother was James III of Scotland. She married twice; firstly to Thomas Boyd, 1st Earl of Arran; secondly to James Hamilton, 1st Lord Hamilton. It was through her children by her second husband that the Hamilton Earls of Arran and Stewart Lennoxes derived their claim to the Kingdom of Scotland.

Family

Mary was born at Stirling Castle on 13 May 1453, the eldest daughter of James II of Scotland and Mary of Guelders. She had five siblings, including James III, who ascended the Scottish throne in 1460 upon their father's accidental death by an exploding cannon. Mary's mother died in 1463, leaving her an orphan at the age of ten.

Marriages and issue

Mary was married to her first husband Thomas Boyd before 26 April 1467 when she was almost fourteen years old. The Isle of Arran was given as her dowry; Thomas Boyd was subsequently created Earl of Arran. Law Castle, in Ayrshire was built for the couple. In 1469, Thomas was sent to escort King James's future consort Princess Margaret from Denmark to Scotland; during his absence the king became alienated from Thomas by the enemies of the Boyd clan who brought false charges of treason against Thomas and his brother, Alexander. Mary, upon hearing that Thomas was to be summoned before the king and Parliament to answer the charges, immediately went to the harbour of Leith to forewarn her husband when his ship docked in July. Mary and Thomas promptly sailed to Denmark. On 22 November 1469 he was attainted, and his title, honours, and estates forfeited to the crown. She later returned to Scotland in an attempt to have her husband cleared of all charges laid against him. Upon her arrival in Scotland, King James detained her in custody in Dean Castle at Kilmarnock until her marriage was annulled. Mary's marriage to Thomas was declared void in 1473.

Thomas and Mary together had two children:

• Margaret Boyd (1468–1516), married firstly, Alexander Forbes, 4th Lord Forbes; secondly Sir David Kennedy, 1st Earl of Cassilis. By her marriage to Sir David Kennedy, she had descendants.
• James Boyd, 2nd Lord Boyd of Kilmarnock (1469–1484)

In early 1474, Mary married secondly as his second wife, James Hamilton, 1st Lord Hamilton, who was almost forty years her senior. They received a papal dispensation on 26 April 1476 thus legitimising the two children already born to them. Together James and Mary had three children:

• James Hamilton, 1st Earl of Arran (1475–1529), married firstly in 1490 Elizabeth Home by whom he had two daughters; he divorced Elizabeth in 1504. He married secondly in 1516, Janet Bethune, daughter of Sir David Bethune, 1st of Creich and Janet Duddlingston. by whom he had three children including his heir, James Hamilton, Duke of Châtellerault, 2nd Earl of Arran (c.1516- 22 January 1575), heir presumptive to the Kingdom of Scotland (2 July 1536 – 22 May 1540), (April 1541- 8 December 1542), (14 December 1542 – 19 June 1566), (29 July 1567 – 22 January 1575); Regent of Scotland (1542–1554)) .
• Hon. Elizabeth Hamilton (died after April 1531), married 9 April 1494 Matthew Stewart, 2nd Earl of Lennox, by whom she had issue. The Lennox Stewarts, of whom Henry Stuart, Lord Darnley, the second husband of Mary, Queen of Scots was the most notable, derived their claim to the Scottish throne from Elizabeth's son John Stewart, 3rd Earl of Lennox.
• Robert Hamilton, Seigneur d'Aubigny (died 1543)

Mary's son by her first husband Thomas, James Boyd, 2nd Lord Boyd of Kilmarnock was killed at the age of fifteen by Lord Montgomerie, which ignited a feud that lasted for over seventy years. Margaret, her daughter by Thomas, lived to the age of forty-eight. Although she was married twice, neither marriage produced children.

Mary died in May 1488 at the age of thirty-five.

Due to their proximity to the throne, Mary's descendants, the Hamiltons of Arran and the Stewart Lennoxes, would obtain considerable power, and play conspicuous roles in 16th century Scottish politics; especially effecting the life and reign of Mary, Queen of Scots, the great-granddaughter of her brother, James III.