William Beresford, 1st Baron Decies (16 April 1743 – 6 September 1819) was an Anglo-Irish clergyman.

Decies was the third son, out of seven sons and eight daughters, of Marcus Beresford, 1st Earl of Tyrone (himself the only son of Sir Tristram Beresford, 3rd Baronet), and Catherine Poer, 1st Baroness de la Poer, the only daughter and heiress of James Power, 3rd Earl of Tyrone and 3rd Viscount Decies.

Elizabeth's brother was John FitzGibbon, 1st Earl of Clare, the Lord Chancellor of Ireland.

[3] Through his third son, he was a grandfather of British Army officer Marcus Beresford (1800–1876), who was also an MP for Northallerton and Berwick-upon-Tweed.

[5] Through his youngest daughter Louisa, he was a grandfather of British MP and patron of the arts, Henry Thomas Hope (1808–1862), whose daughter Henrietta married Henry Pelham-Clinton, 6th Duke of Newcastle, and British MP Alexander Beresford Hope (1820–1887), who married Lady Mildred Gascoyne-Cecil (a daughter of James Gascoyne-Cecil, 2nd Marquess of Salisbury).