| Honorific Prefix: | The Right Honourable |
| The Earl of Erroll | |
| Office: | Lord High Commissioner |
| Term Start: | 1817 |
| Term End: | 1819 |
| Predecessor: | The Lord Napier |
| Successor: | The Earl of Morton |
| Birth Name: | William Hay |
| Birth Date: | 12 March 1772 |
| Parents: | James Hay, 15th Earl of Erroll Isabella Carr |
| Spouse: | |
| Children: | 11, including James and William |
| Relatives: | William Boyd, 4th Earl of Kilmarnock (grandfather) |
William Hay, 17th Earl of Erroll (12 March 1772 – 26 January 1819), known as Lord Hay until 1778, was a Scottish peer.[1]
Erroll was the son of James Hay, 15th Earl of Erroll and his second wife, Isabella Carr, the eldest daughter and co-heiress of William Carr of Etal in Northumberland. His elder sister, Lady Augusta Hay (the first wife George Boyle, 4th Earl of Glasgow), succeeded to the Etal estate in 1806. From his father's first marriage to Rebecca Lockhart, he had one half-sibling, Lady Mary Hay, who married Gen. John Scott of Balcomie.
His paternal grandparents were William Boyd, 4th Earl of Kilmarnock and Lady Anne Livingston (a daughter of James Livingston, 5th Earl of Linlithgow).[2]
In 1798, he succeeded to the earldom of Erroll following the death of his elder brother George, who died without issue.
In 1805, he was appointed Knight Marischal of Scotland, serving until 1809.[3] He also served as a Scottish representative peer (Whig) from 1806 to 1807 and, again, from 1818 to 1819.
From 1817 to 1819, he was Lord High Commissioner to the General Assembly of the Church of Scotland.
He firstly married Jane Bell (d. 1793), the second daughter of Matthew Bell of Wolsingham.[4] in 1792. Before her death in 1793, they had one child together:
Secondly, he married Alicia Eliot (d. 1812), the third daughter of Samuel Eliot, Esq. of Antigua, and Alice (née Byam) Eliot (a daughter of Col. William Byam of Antigua), in 1796. Alicia was the sister-in-law of Sir Thomas Stapleton, 6th Bt. (also the 16th Baron Le Despencer). Together, they were the parents of seven children, including:
In 1816, he married, thirdly, to Harriet Somerville (d. 1864), sister of Mark Somerville, 16th Lord Somerville and third daughter of Lt.-Col. Hon. Hugh Somerville (second son of James Somerville, 13th Lord Somerville), by his second wife, Mary Digby (eldest daughter of Hon. Wriothesley Digby, son of William Digby, 5th Baron Digby). They were the parents of three children, including:
Lord Erroll died on 26 January 1819 and was succeeded by his eldest surviving son, William. His widow, the Dowager Countess of Erroll, died in 1864.[5]