John Allen may refer to:

• John Allen (historian) (1771–1843), Scottish historian and political writer
• John Allen (bookseller) (1789–1829), English bookseller and antiquary
• John S. Allen (1907–1982), American university president

• John Allen (miner) (1775–?), English lead miner aboard HMS Investigator
• John Allen (trade unionist) (1804–1888), Irish trade union leader
• John Allen (saloon keeper) (1823–1870), American saloon keeper and underworld figure in New York City

• John Allen (soldier) (1771–1813), American Army officer killed in the War of 1812
• John Melville Allen (c. 1798–1847), American soldier; philhellene; first mayor of Galveston, Texas
• John Allen (Irish nationalist) (c. 1780–1855), Irish nationalist and colonel in the French army
• John Allen (RAF officer) (1916–1940), British flying ace of the Second World War
• John R. Allen Jr. (born 1935), United States Air Force general
• John R. Allen (born 1953), United States Marine Corps general
• John J. Allen (general), United States Air Force general

• John Southgate Allen (1883–1955), member of the New Zealand Legislative Council
• John Manchester Allen (1901–1941), New Zealand politician
• John Allen (diplomat) (fl. 2009–2011), Administrator of Tokelau

• John Allen, 1st Viscount Allen (1660–1726), Irish peer and politician
• John Allen, 3rd Viscount Allen (1713–1745), Irish peer and politician
• John Allen, 4th Viscount Allen (died 1753), Irish peer and politician
• John Hensleigh Allen (1769–1843), English politician; Member of Parliament for Pembroke
• Sir John Sandeman Allen (Liverpool West Derby MP) (1865–1935), British politician; Member of Parliament for Liverpool West Derby
• John Sandeman Allen (Birkenhead West MP) (1892–1949), British politician; Member of Parliament for Birkenhead West

• John Allen (Connecticut politician) (1763–1812), U.S. Representative from Connecticut
• John J. Allen (judge) (1797–1871), American jurist and U.S. Representative from Virginia
• John W. Allen (1802–1887), American politician; mayor of Cleveland, Ohio
• John Kirby Allen (1810–1838), American politician in the Texas House of Representatives; founder of Houston
• John J. Allen (New York politician) (1842–1926), American politician in the New York State Assembly
• John Howard Allen (1845–1942), American politician; mayor of Orlando, Florida
• John B. Allen (1845–1903), American politician; first U.S. Senator from Washington
• John Mills Allen (1846–1917), U.S. Representative from Mississippi
• John Clayton Allen (1860–1939), U.S. Representative from Illinois
• John E. Allen (judge) (1873–1945), justice of the New Hampshire Supreme Court
• John J. Allen Jr. (1899–1995), U.S. Representative from California
• John Allen (Arizona politician), American politician and member of the Arizona House of Representatives

• John Campbell Allen (1817–1898), Canadian justice of the colonial New Brunswick Supreme Court
• John J. Allen (Canadian politician) (1871–1935), Canadian politician; mayor of Ottawa
• William John Allen, Canadian politician

• John Allin (Puritan minister) (1596–1671), or Allen, English born Puritan cleric in Massachusetts
• John Allen (minister) (1741/2–1780s), English Baptist minister who supported the independence of America
• John Allen (religious writer) (1771–1839), English dissenting layman and religious writer
• John Allen (archdeacon of Chester) (died 1695)
• John Allen (archdeacon of Salop) (1810–1886), Welsh cleric
• John Allen (provost of Wakefield) (1932–2015), English Anglican Provost of Wakefield Cathedral
• John L. Allen Jr. (born 1965), American religion journalist

• John Allen (engineer) (born 1928), English engineer and plasma physicist
• John Allen (physician) (c. 1660–1741), English physician and inventor
• John F. Allen (biochemist) (born 1950), British biochemist
• John F. Allen (physicist) (Jack Allen, 1908–2001), Canadian physicist who worked on superfluid helium
• John P. Allen (born 1929), American ecologist and engineer; co-founder of the Biosphere 2 Center
• John R. L. Allen (1932–2020), British geologist
• John Romilly Allen (1847–1907), British archaeologist
• John T. Allen, Australian atmospheric scientist

• John Allen (baseball) (1890–1967), American baseball player
• Hap Allen (John Francis Allen Jr., 1900–1988), American baseball player
• John Allen (athlete) (1926–2006), American Olympic athlete
• John Allen (rugby union) (1942–2022), English rugby union player
• John Allen (footballer, born 1955), English footballer
• John Allen (hurler) (born 1955), English hurling player and manager
• John Allen (footballer, born 1964), English footballer for Chester City and Mansfield Town
• John Allen (American football) (fl. 1970s), American football coach
• John Allen (sportsman, born 1974), Australian rugby union player and cricketer
• John Allen (basketball) (born 1982), American basketball player
• John Allen (American football coach, SAGU) (born c. 1962), American football coach (SAGU 1996–1997)

• John Allen (settler) (1806–1879), English settler in the colony of Van Diemen's Land (later Tasmania)
• John Allen (pioneer) (1796–1851), American pioneer and co-founder of Ann Arbor, Michigan
• John Allen, Welsh paedophile at the centre of the North Wales child abuse scandal
• John C. Allen (1907–1979), American roller coaster designer
• John Whitby Allen (1913–1973), American pioneering model railroader
• John Allen (murderer) (1934–2015), English criminal who murdered his wife and children
• John P. Allen (musician), Canadian country, rock and bluegrass fiddler
• John Allen (guitarist), member of The Nashville Teens

• Allen (surname)
• Jack Allen (disambiguation)
• John Allan (disambiguation)
• Johnny Allen (disambiguation)
• Jon Allen (disambiguation)
• John Alen (1476–1534), English priest and canon lawyer
• John Alleyn (disambiguation), including John Alleyne
• John Allin (1921–1998), American Episcopalian bishop