| Honorific Prefix: | The Right Honourable |
| The Earl of Erroll | |
| Office: | Rector of the University of Glasgow |
| Term Start: | 1761 |
| Term End: | 1763 |
| Predecessor: | James Milliken of Milliken |
| Successor: | Thomas Miller |
| Birth Name: | James Boyd |
| Birth Date: | 20 April 1726 |
| Birth Place: | Falkirk, Stirlingshire, Scotland |
| Party: | Tory |
| Spouse: | |
| Parents: | William Boyd, 4th Earl of Kilmarnock Anne Livingston of Erroll |
| Children: | 13, including George and William |
James Hay, 15th Earl of Erroll (20 April 1726 – 3 June 1778 (Chester Courant, 16 June 1778)) styled Lord Boyd from 1728 to 1746, was a Scottish nobleman and the son of William Boyd, 4th Earl of Kilmarnock.After his father was attainted in 1746, he became Mr James Boyd, but in 1758 he inherited the Earldom of Erroll from a great-aunt.
He was born James Boyd at Falkirk on 20 April 1726, the eldest son of William Boyd, 4th Earl of Kilmarnock, and his wife Lady Anne Livingston. She was the only daughter of James Livingston, 5th Earl of Linlithgow, a Jacobite attainted for his role in the 1715 Rising, and Lady Margaret Hay, the second daughter of John Hay, 12th Earl of Erroll.
From 1728 to 1746, Erroll was known by the courtesy title of Lord Boyd, while his father was Earl of Kilmarnock.
During the 1745 Jacobite Rebellion his father sided with the Young Pretender, despite both of his sons, James and William Boyd, then holding commissions under King George II; James Boyd in the British army, his brother in the Royal Navy. Remaining loyal to the Hanoverians, James Boyd fought at the Battle of Culloden on the opposite side to his father.[1] During the rout following the Jacobite defeat, the Earl of Kilmarnock was captured and taken prisoner, dishevelled and bareheaded, and was reportedly recognised by his son James, who placed his own hat on his father's head.[2] This was the last time they were to meet, as Kilmarnock was then transported to London, tried for treason, and executed four months later; forfeiting all his lands and titles, which deprived his son of his inheritance.
In 1751, however, although the Earldom remained forfeit, James Boyd was allowed to inherit the Kilmarnock estates. These included Dean Castle, the former family seat which had been gutted by a fire in 1735. Trying to cover some of his father's debts, which he had also inherited, James Boyd sold the ruined castle to the 13th Earl of Glencairn. From 1751 to 1752, he served as Grand Master of the Grand Lodge of Scotland.
On 19 August 1758, James Boyd succeeded his maternal great-aunt, Mary Hay, 14th Countess of Erroll, as Earl of Erroll, simultaneously changing his surname from Boyd to Hay, as he and his descendants were henceforth to be known. Along with the title Earl of Erroll, he also held the ceremonial hereditary office of Lord High Constable of Scotland.[3]
Between 1770 and 1774, he served as a Tory Scottish representative peer in the House of Lords, and from 1770 to 1778, he was Lord of Police for Scotland.
On 15 September 1749, he married Rebecca Lockhart, the daughter of Alexander Lockhart, Lord Covington. Before her death in 1761, they were the parents of one daughter:
In 1762, he married Isabella Carr (1747–1808), daughter of Sir William Carr of Etal, Northumberland. Together, they were the parents of twelve children, including:
Lord Erroll died on 3 June 1778 at Callendar House, aged fifty-two, and was succeeded by his eldest son, George.[4] His widow died 3 November 1808.[5]
Lord Erroll's grandson, William Hay, 18th Earl of Erroll, was created Baron Kilmarnock in the peerage of the United Kingdom in 1831.[5] [6]