William Wellesley-Pole, 3rd Earl Of Mornington

William Wellesley-Pole, 3rd Earl of Mornington (20 May 1763 – 22 February 1845), was an Anglo-Irish politician and a member of the Wellesley family. He was known as Lord Maryborough from 1821 until 1842, when he succeeded to the earldom.

Born William Wesley at Dangan Castle, he was the second son of Garret Wesley, 1st Earl of Mornington, and Annie Hill, daughter of Arthur Hill-Trevor, 1st Viscount Dungannon. He had several siblings, including Richard Wesley (later Marquess Wellesley), Arthur Wellesley (later Duke of Wellington), and Henry Wesley (later Lord Cowley).

He received education at Eton College from 1774 to 1776. Subsequently, he served in the Royal Navy as a midshipman from 1777 to 1783, participating aboard HMS Lion and involved in the Battle of Grenada in 1779.

In 1781, due to his family's financial difficulties and inheritance from William Pole of Ballyfin, he adopted the surname Wesley-Pole, in accordance with the will of William Pole and the tradition of family name changes after inheritances. William Pole was descended from Sir William Pole of Shute House, Devon, and his marriage to Ann Colley connected him to the Wesley family through her sister, Ann Colley, wife of William Pole; she was the aunt of William Wesley's grandfather, Richard Wesley, who had changed his surname from Richard Colley to Wesley in 1728.

Politically, Mornington was a Tory. He served as a Member of the Irish Parliament for Trim (1783–1790), and as a Member of the British House of Commons for East Looe (1790–1795) and Queen's County (1801–1821). His governmental roles included Secretary of the Admiralty under the Duke of Portland (1807–1809), Chief Secretary for Ireland under Spencer Perceval (1809–1812), and positions within Irish administration such as Lord of the Irish Treasury (1809–1811) and Chancellor of the Irish Exchequer (1811–1812). He was sworn into both the British Privy Council and the Irish Privy Council in 1809.

Between 1814 and 1823, he served as Master of the Mint under the government of Lord Liverpool. In 1821, he was elevated to the Peerage of the United Kingdom as Baron Maryborough of Maryborough in Queen's County. In 1823, he was appointed Custos Rotulorum of Queen's County for life. His additional offices included Master of the Buckhounds (1823–1830), Postmaster General (1834–1835), and Captain of Deal Castle from 1838.

Following the death of his elder brother, Richard Wellesley, 1st Marquess Wellesley, in 1842, he inherited the title of Earl of Mornington, becoming the 3rd Earl.

On 24 June 1784, William Wellesley-Pole married Katherine Elizabeth Forbes, daughter of Admiral John Forbes and granddaughter of George Forbes, 3rd Earl of Granard, and William Capell, 3rd Earl of Essex. Their marriage produced one son and three daughters:

- William Pole-Tylney-Long-Wellesley (1788–1857), who succeeded as the 4th Earl of Mornington and married Catherine Tylney-Long.

- Lady Mary Charlotte Anne Wellesley (1786–1845), who married Sir Charles Bagot, Bart., G.C.B., and served as ‘Her Excellency’ in Montreal during her husband's appointment as Governor-General of British North America.

- Lady Emily Harriet Wellesley (1792–1881), married Lord FitzRoy Somerset, later 1st Baron Raglan.

- Lady Priscilla Anne Wellesley (1793–1879), married John Fane, later 11th Earl of Westmorland.

William Wellesley-Pole died on 22 February 1845.