Colonel The Hon. William Le Poer Trench CVO, JP (17 June 1837 – 16 September 1920) was an Anglo-Irish politician and British army officer.

He was the third son of William Trench, 3rd Earl of Clancarty and Lady Sarah Juliana Butler.

He married Harriet Maria Georgina Martins, daughter of Sir William Martins, on 21 April 1864.

He fought in the Second Opium War between 1857 and 1858, commanding a ladder company at the capture of Guangzhou and Nankow, and was mentioned in despatches. He gained the rank of Colonel in the service of the Royal Engineers.

Between 1872 and 1874, he was Member of Parliament (MP) for County Galway, having unseated the elected MP, John Philip Nolan, on petition; the case was one of the most controversial Irish cases of its time and permanently damaged the reputation of the judge, William Keogh.

He held the office of Justice of the Peace for Westminster, London, Buckinghamshire, and Middlesex. He was made a Commander of the Royal Victorian Order in 1912.^[1]