Boyle was born in Castlemartyr, the second son of Lieutenant-Colonel Henry Boyle (1648–1693), second son of Roger Boyle, 1st Earl of Orrery and Lady Margaret Howard. His mother was Lady Mary O'Brien, daughter of Murrough O'Brien, 1st Earl of Inchiquin and Elizabeth St. Leger. His father died during the Flanders campaign of 1693. On the death of Henry's eldest brother Roger in 1705 he succeeded to the family estates at Castlemartyr, which he found to be in a state of serious neglect. Henry did much to improve the estate and Castlemartyr village. He also managed the County Cork estates of his second wife's father, Lord Burlington, and proved himself an excellent steward of the family property.
In 1707, he was elected to the Irish House of Commons for Midleton, a seat he held until 1713, and then sat for Kilmallock from 1713 to 1715. Between 1715 and 1756 he represented County Cork. He quickly gained a prominent role in Parliament and Sir Robert Walpole is said to have styled him "the King of the Irish House of Commons". In 1733 Boyle was admitted to the Irish House of Commons and appointed Chancellor of the Irish Exchequer. Later that year he was also made Speaker of the Irish House of Commons. His career was marked by a long struggle for power with George Stone, Archbishop of Armagh, which only ended with their deaths in the same week. He deserves some credit for helping to organise measures to alleviate the terrible Irish Famine (1740–41) which was long remembered as "the year of slaughter".
He held the posts of Speaker and Chancellor until 1753, when he was dismissed by the viceroy Lord Dorset for refusing to pay over an Irish tax surplus to the government in London. This led to the "Money Bill dispute" of 1753-56, and Boyle came to be seen as an early Irish patriot. Reinstated in 1755 by Devonshire, the next viceroy, in 1756 he was raised to the Peerage of Ireland as Baron Castle Martyr, Viscount Boyle, of Bandon, and Earl of Shannon. He also acted several times as Lord Justice of Ireland.
Horace Walpole dismissed him as a "common character" who sold his patriotism for a peerage.
Lord Shannon married Catherine Coote, daughter of Colonel Chidley Coote of Kilmallock and Catherine Sandys, in 1715. They had no issue. After her death in 1725, he married Lady Henrietta Boyle, youngest daughter of Charles Boyle, 3rd Earl of Cork and 2nd Earl of Burlington and Juliana Noel, in 1726.
Lord Shannon died in December 1764, in his 82nd year, and was succeeded in his titles by his son from his second marriage, Richard Boyle, 2nd Earl of Shannon.
- Stephen, Leslie, ed. (1886). . Dictionary of National Biography. 6. London: Smith, Elder & Co.
- Kidd, Charles; Williamson, David (editors) (1990). Debrett's Peerage and Baronetage. New York: St Martin's Press.CS1 maint: extra text: authors list (link)
|Parliament of Ireland|
St John Brodrick
| Member of Parliament for Midleton
With: Robert Foulke
| Member of Parliament for Kilmallock
With: Sir Philips Coote
| Member of Parliament for Cork County
With: St John Brodrick 1715–1728
Sir Matthew Deane, 3rd Bt 1728–1747
Arthur Hyde 1747–1756
Charles Boyle, Viscount Dungarvan
| Speaker of the Irish House of Commons
|Peerage of Ireland|
|New creation|| Earl of Shannon