John Sullivan may refer to:

• John Earle Sullivan (born 1994), American political activist and convicted participant in the January 6 United States Capitol attack
• William John Sullivan (born 1976), usually known as John Sullivan, free software activist

• John Sullivan (Jesuit) (1861–1933), Irish priest, Catholic Blessed in the Altars
• John Joseph Sullivan (bishop) (1920–2001), American clergyman of the Roman Catholic Church

• John Sullivan (writer) (1946–2011), English screenwriter for sitcoms including Only Fools and Horses, Citizen Smith and Just Good Friends
• Fred Allen (John Florence Sullivan), American radio comedian
• John Jeremiah Sullivan (born 1974), American writer and editor
• John L. Sullivan (elephant) (c. 1860–1932), boxing elephant of the Adam Forepaugh Circus

• John M. Sullivan (mathematician) (born 1963), American mathematician
• John W. Sullivan, mathematician and member of the Palliser Expedition

• John Sullivan (Australian politician) (born 1929), Australian politician
• John Sullivan (colonial administrator) (1788–1855), district collector of Coimbatore, southern India
• John Sullivan (MP) (1749–1839), British Privy Counsellor, MP for Aldborough, Ashburton and Old Sarum
• John Sullivan (Oklahoma politician) (born 1965), United States Representative from Oklahoma
• John Alexander Sullivan (1879–1952), Conservative member of the Canadian House of Commons
• John Andrew Sullivan (1868–1927), United States Representative from Massachusetts
• John Augustus Sullivan (1798–1871), Jamaican politician
• John B. Sullivan (1897–1951), United States Representative from Missouri
• John J. Sullivan (diplomat) (born 1959), former US Ambassador to Russia, former Deputy Secretary of State and Deputy Secretary of Commerce
• John J. Sullivan (Massachusetts politician), running mate of Christy Mihos
• John L. Sullivan (Arizona politician), Arizona Attorney General, 1935–1937 and 1944–1948
• John L. Sullivan (United States Navy) (1899–1982), United States Secretary of the Navy
• John Leo Sullivan, Secretary of State for the U.S. state of Missouri, 1917–1921
• John M. Sullivan (politician) (born 1959), Illinois state senator
• John P. Sullivan (politician) (1843–1899), merchant and politician in Prince Edward Island, Canada

• John Sullivan (American sailor) (1839–1913), American Civil War sailor and Medal of Honor recipient
• John Sullivan (general) (1740–1795), United States general and delegate to the Continental Congress, Governor of New Hampshire and federal judge
• John Sullivan (VC) (1830–1884), Irish sailor who won the Victoria Cross
• John P. Sullivan (general), United States Army general

• John Sullivan (1900s catcher) (1873–1924), MLB catcher from 1905 to 1908
• John Sullivan (outfielder) (1890–1966), MLB outfielder from 1920 to 1921
• John Sullivan (pitcher) (1894–1958), MLB pitcher in the 1919 season
• John Sullivan (shortstop) (1920–2007), MLB shortstop from 1942 to 1949
• John Sullivan (1960s catcher) (1941-2023), MLB catcher from 1963 to 1968

• John Sullivan (Lancashire cricketer) (1945–2006), English cricketer
• John Sullivan (Gloucestershire cricketer) (1948–2023), English cricketer

• John Sullivan (English footballer) (born 1988), English goalkeeper with Portsmouth F.C.
• John Sullivan (Irish footballer) (born 1991), Irish midfielder with Drogheda United F.C.

• John Sullivan (Canadian football) (born 1981), Canadian football player
• John Sullivan (center) (born 1985), American football player
• John Sullivan (kicker) (born 1985), American football player
• John Sullivan (defensive back) (born 1961), American football defensive back
• John Sullivan (American football coach) (1938–2010), American football player and coach

• John Sullivan (racehorse trainer), American Thoroughbred racehorse trainer
• John Sullivan (shot putter), silver medalist in the shot put at the 2000 African Championships in Athletics
• JT Sullivan (born 1988), full name John Sullivan, All-American steeplechase runner for the Stanford Cardinal track and field team
• John Sullivan (tennis) (born 1966), American tennis player
• John L. Sullivan (1858–1918), Irish-American boxer and first heavyweight boxing champion
• John L. Sullivan (wrestler) (born 1946), professional wrestler better known as Johnny Valiant
• John F. Sullivan (1935–2010), player in the American Basketball League

• John C. Sullivan (died 1830), surveyor who established the eastern border of Indian Territory
• John Joseph Sullivan (judge) (1855–1926), Chief Justice of the Nebraska Supreme Court
• John Sullivan (1793–1867), member of the Stephens-Townsend-Murphy Party, the first wagon train to cross the Sierra Nevadas into California
• John P. Sullivan (USN), author of Volume I of the Dictionary of American Naval Fighting Ships

• John L. Sullivan, lead character in Preston Sturges's Sullivan's Travels, played by Joel McCrea
• John Sullivan, lead character in Frequency, played by Jim Caviezel
• John "Sully" Sullivan, character in Third Watch, played by Skipp Sudduth
• John Sullivan, character in 40 Days and 40 Nights
• John Sullivan, character in Around the World in Eighty Days
• John Sullivan, lead character in "Something Was Wrong" from More Scary Stories to Tell in The Dark

• Jon Sullivan (1950–2021), Australian politician
• Jack Sullivan (disambiguation)
• John O'Sullivan (disambiguation)