John Arnold may refer to:

Politicians

• John Arnold (Kentucky politician), member of the Kentucky House of Representatives, 1995–2013
• John Arnold (MP for Ipswich) (died 1410), MP for Ipswich, 1388–1399
• John Arnold (MP for Hampshire) (died 1433), MP for Hampshire, 1413
• John Arnold (MP for Monmouthshire) (died 1606), MP for Monmouthshire, 1597
• John Arnold of Monmouthshire (c. 1635–1702), Ultra-Protestant and MP for Monmouth, 1680–1689, 1695 and Southwark, 1689–1695
• John H. Arnold (politician) (1862–1944), American politician; Lieutenant Governor of Ohio, 1915–1917
• John W. Arnold (1842–1900), American politician; Illinois Senate, 1890–1894

Music

• John Arnold (1720–1792), English music editor and composer of psalmodies in the West Gallery style
• John Dent Arnold (1890–1948), American lyricist with composer Harry Baisden of World War I songs
• John Ayldon (John Arnold, 1943–2013), English opera singer

Others

• John Arnold (American football) (born 1955), American football player
• John Arnold (bishop) (born 1953), English Catholic bishop
• John Arnold (cinematographer) (1889–1964), American cinematographer
• John Arnold (judge) (1915–2004), British judge
• John Arnold (priest) (born 1933), Anglican dean and author
• John Arnold (watchmaker) (1736–1799), English watchmaker and inventor, with a son named John Roger Arnold (1769–1843)
• John D. Arnold (born 1974), former Enron trader and political activist
• John E. Arnold (1913–1963), American psychologist and engineer
• John H. Arnold (historian) (born 1969), British historian and professor
• John Nelson Arnold (1834–1909), American portrait painter
• John Arnold, Australian surf entrepreneur, behind Golden Breed
• John Arnold, a character in the novel Jurassic Park
• John Arnold, perpetrator of the murder of Betty Gardner
• Johnny Arnold (1907–1984), English international footballer and test cricketer