William Mayne, 1st Baron Newhaven
William Mayne, 1st Baron Newhaven PC (1722 – 28 May 1794), known as Sir William Mayne, Bt, between 1763 and 1776, was a British politician.
Mayne was the eldest son of the second marriage of William Mayne, of Powis Logie, Clackmannanshire. He was returned to the Irish House of Commons in 1761 for Carysfort, a seat he held until 1776. He was created a Baronet, of Marston Mortaine in the County of Bedford, in the Baronetage of Great Britain in 1763 and sworn of the Irish Privy Council in 1766. In 1774 he was elected to the British House of Commons for Canterbury. Two years later he was elevated to the Peerage of Ireland as Baron Newhaven, of Carrick Mayne in the County of Dublin. He continued to represent Canterbury until 1780 and then sat for Gatton until 1790.
Lord Newhaven married the Honourable Frances Allen, daughter of Joshua Allen, 2nd Viscount Allen, and co-heir of her brother John Allen, 3rd Viscount Allen, through which marriage he gained a considerable estate. They had one son who died in infancy. Lord Newhaven died in May 1794 when the baronetcy and barony became extinct.
- Burke, John. Burke, John Bernard. A Genealogical and Heraldic History of the Extinct and Dormant Baronetcies of England, p. 348.
- leighrayment.com Irish House of Commons 1692–1800
- The London Gazette: . 12 April 1763.
- leighrayment.com Privy Counsellors
- Leigh Rayment's Historical List of MPs – Constituencies beginning with "C" (part 2)[self-published source][better source needed]
- The London Gazette: . 29 June 1776.
- Leigh Rayment's Historical List of MPs – Constituencies beginning with "G" (part 1)[self-published source][better source needed]
|Parliament of Ireland|
|Member of Parliament for Carysfort
With: Sir William Osborne, Bt 1761–1769
Sir Robert Deane, Bt 1769–1771
Sir Robert Deane, Bt 1771–1776
|Parliament of Great Britain|
|Member of Parliament for Canterbury
With: Richard Milles
|Member of Parliament for Gatton
With: Robert Mayne 1780–1782
Maurice Lloyd 1782–1787
James Fraser 1787–1790
|Baronetage of Great Britain|
(of Marston Mortaine)
|Peerage of Ireland|
|New creation||Baron Newhaven