William Trench, 3rd Earl of Clancarty
William Thomas Le Poer Trench, 3rd Earl of Clancarty, 2nd Marquess of Heusden, styled Viscount Dunlo between 1805 and 1837, was an Irish peer, as well a nobleman in the Dutch nobility. He was educated at St John's College, Cambridge.
Trench was born in Castleton, County Kildare, Ireland the son of Richard Trench, 2nd Earl of Clancarty and Henrietta Margaret Staples. On 8 September 1832, he married Lady Sarah Juliana Butler. They had six children.
- Richard Somerset Le Poer Trench, 4th Earl of Clancarty married Lady Adeliza Georgiana Hervey
- Major Hon. Frederick Le Poer Trench married Harriet Mary Trench Catherine Simpson
- Colonel William Le Poer Trench married Harriet Maria Georgina Martins
- Lady Anne Le Poer Trench married Frederic Sydney Charles Trench
- Power Henry Le Poer Trench
- Lady Sarah Emily Grace Le Poer Trench married John Melville Hatchell.