William Caulfeild, 2nd Viscount Charlemont
William Caulfeild, 2nd Viscount Charlemont PC (c.1655 – 21 July 1726) was an Irish soldier and peer.
Caulfeild was the son of William Caulfeild, 1st Viscount Charlemont of County Armagh, whom he succeeded in 1671.
He was an avid pro-Williamite in the struggle between William of Orange and King James II of England for the British crown, and was consequently attainted by King James' first Parliament in 1689. He was rewarded by William for his loyalty by being put in command of a regiment of infantry and created Custos Rotulorum of Tyrone and Armagh. After Willams's victory the regiment was disbanded but in 1701 he was given command of the new 36th Foot Regiment and promoted in 1704 to the rank of Brigadier-General. He took the regiment to Spain, taking part in the Siege of Barcelona and the attack on Fort Montjuïc in 1705. Although contentiously removed from his command of the regiment, he was nevertheless promoted in 1707 to the rank of Major-General and made Governor of Counties Armagh and Tyrone. 
In May 1726, he was made a Privy Counsellor but died shortly afterwards and was buried in the vault of the family in Armagh. He had married Anne, the only daughter of James Margetson, Archbishop of Armagh and with her had five sons and seven daughters. He was succeeded by James, his eldest surviving son.  Another son, Thomas, was an early British Lieutenant-Governor of Nova Scotia. One of Caulfeild's granddaughters, Sophia Frances Anne Caulfeild, was an author, poet and encyclopedist.
- "Colonel of the 36th Regiment of Foot (became 2nd Battalion Worcestershire Regiment in 1881)". Retrieved 30 June 2014.
- Biographia Hibernica: a biographical dictionary of the worthies of Ireland.
- Henderson 1887, p. 328.
- Burke, John. A General and Heraldic Dictionary of the Peerage and Baronetage of the British Empire. 2. p. 230.
- A Genealogical and Heraldic Dictionary of the Peerage and Baronetage of the ... p. 193. Retrieved 12 November 2014.