John Slater may refer to:

• John Slater (industrialist) (1776–1843), (American) father of John Fox Slater, brother and partner of Samuel Slater
• John Fox Slater (1815–1884), American philanthropist, son of John Slater (industrialist)
• John Slater (art director) (1877–1914), art director at Doulton's Burslem factory
• John Slater (New Zealand politician), former President of the New Zealand National Party and current President of Citizens and Ratepayers Now
• John Slater (British politician) (1889–1935), British Conservative MP for Eastbourne, 1932–1935
• John Slater (Canadian politician) (1952–2015), Member of the Legislative Assembly of British Columbia
• John J. Slater Jr. (1925–1998), American lawyer and politician in Massachusetts
• John Slater & Co. of Forestdale, Rhode Island

• John C. Slater (1900–1976), American physicist and theoretical chemist
• J. D. Slater (born 1954 or 1955), filmmaker and composer
• John Slater (actor) (1916–1975), British actor specialising in Cockney parts
• John Slater (cricketer) (1795–?), English cricketer
• John Slater (figure skater) (1935–1989), British figure skater and ice dancer
• John Slater, former guitarist with Blaze Bayley
• John Slater (trade unionist) (1920–1974), British trade union leader
• John Samuel Slater (1850–1911), British professor of civil engineering