William Pole-Tylney-Long-Wellesley, 5th Earl of Mornington

William Richard Arthur Pole-Tylney-Long-Wellesley, 5th Earl of Mornington (7 October 1813 – 25 July 1863) was a British nobleman.

Long-Wellesley, the son of the notorious spendthrift William Pole-Tylney-Long-Wellesley (later fourth Earl of Mornington) and Catherine Tylney-Long (daughter of Sir James Tylney-Long, 7th Baronet), was born on 7 October 1813 at Wanstead House, at that time in Essex, but within the London borough of Redbridge since 1965.

William junior maintained that these items belonged to him as heirlooms by the will of Sir James Long, 2nd Baronet.

In 1848, despite opposition from his father, he sold Athelhampton which had been purchased by Sir Robert Long, 1st Baronet, in 1665.

Mornington died unmarried in Paris on 25 July 1863 from cancer of the tongue, and is buried at Draycot Cerne in Wiltshire.

The 5th Earl was the last noble to bear the title as their most senior title; its successor was the 2nd Duke of Wellington and it would have devolved to the 1st Duke so will stay a secondary title of the Dukes, seldom if ever used, until the Dukedom becomes extinct.
Wall monument to the Earl at the church of Draycot Cerne , by Triqueti