Businessmen

• John Williams (football executive) (born 1939 or 1940), English football executive
• John Williams (winemaker) (born 1953), American winemaker
• John C. Williams (economist) (born 1962), president and chief executive officer of the Federal Reserve Bank of New York
• John H. Williams (businessperson), American businessperson
• John Henry Williams (baseball) (1968–2004), son of baseball player Ted Williams
• John Osborn Williams (1886–1963), Canadian businessperson
• John P. Williams Jr. (1941–2019), president of the Greater Cincinnati Chamber of Commerce
• John Stanton Williams (1814–1876), American shipowner and businessperson

Clergymen

• John Williams (Ab Ithel) (1811–1862), Welsh antiquary and Anglican priest
• John Williams (archbishop of York) (1582–1650), British Anglican archbishop of York and political advisor to King James I
• John Williams (archdeacon of Switzerland) (born 1948), Anglican archdeacon of Switzerland
• John Williams (archdeacon of Worcester) (1912–2002), Anglican archdeacon of Dudley and archdeacon of Worcester
• John Williams (bishop of Chichester) (1636–1709), English bishop of Chichester
• John Williams (bishop of Connecticut) (1817–1899), American bishop of Connecticut, presiding bishop of the Episcopal Church, and dean of Berkeley Divinity School
• John Williams (dean of Llandaff) (1907–1983), Welsh Anglican archdeacon of Llandaff and dean of Llandaff
• John Williams (evangelical priest) (1762–1802), Welsh Anglican priest
• John Williams (minister and physician) (1626 or 1627 – 1673), Welsh nonconformist preacher and physician
• John Williams (missionary) (1796–1839), English Congregationalist missionary eaten by cannibals in Vanuatu
• John Williams (New England minister) (1664–1729), New England Puritan minister, famous for The Redeemed Captive
• John Williams (Oxford academic) (died 1613), British Anglican dean of Bangor, principal of Jesus College, Oxford, and vice-chancellor of the University of Oxford
• John Williams (priest, born 1792) (1792–1858), Welsh Anglican archdeacon of Cardigan, scholar, and schoolmaster
• John Williams (schoolmaster, born 1760) (1760–1826), Welsh Anglican priest and schoolmaster
• John Albert Williams (1866–1933), American Episcopal priest, journalist, and political activist
• Chris Williams (bishop) (John Christopher Richard Williams, born 1936), Anglican bishop in Canada
• John Elias Williams (1871–1927), American Presbyterian missionary to China
• John Joseph Williams (1822–1907), American Roman Catholic archbishop of Boston
• John Owen Williams (Pedrog) (1853–1932), Welsh Congregationalist minister and poet
• John Tudno Williams (born 1938), moderator of the Presbyterian Church of Wales and principal of United Theological College, Aberystwyth

Criminals and alleged criminals

• John Williams (British mass murderer) (1774–1811), perpetrator of the Ratcliff Highway murders
• John Williams (convict), convict transported to Van Diemen's Land (now Tasmania)
• John Williams (died 1913), murder convict in the Case of the Hooded Man
• John Allen Williams (murderer) or John Allen Muhammad (1960–2009), American murderer
• Johnny Madison Williams Jr. (born 1951), bank robber

Judges

• John Williams (English judge) (died 1846), known for the 1830s Tolpuddle Martyr trials
• John A. Williams (judge) (1835–1900), US federal judge
• John Griffith Williams (born 1944), Welsh judge of the High Court of England and Wales
• Hugh Williams (judge) (John Hugh Williams, born 1939), New Zealand judge
• B. John Williams (born 1949), American lawyer and judge

Military figures

Musicians

• John Williams (bassist) (born 1941), American jazz double bassist, bass guitarist
• John Williams (guitarist) (born 1941), Australian classical guitarist
• John Williams (pianist) (1929–2018), American jazz pianist
• John B (John Bryn Williams, born 1977), English disc jockey
• John David (musician) (John David Williams, born 1946), Welsh pop and rock musician and songwriter
• John Gary Williams (fl. 1960–1990), American R&B singer and member of The Mad Lads
• John McLaughlin Williams (born 1957), American classical conductor and violinist
• John Overton Williams (1905–1996), American jazz saxophonist with Andy Kirk
• John Owen Williams (record producer) (born 1951), English A&R executive, record producer and songwriter
• Johnny Williams (bassist) (1908–1998), American jazz double bassist
• Johnny Williams (blues musician) (1906–2006), Chicago blues guitarist and singer
• Johnny Williams (drummer) (1905–1985), American jazz drummer with the Raymond Scott Quintette
• Johnny Williams (saxophonist) (1936–1998), American saxophonist with Count Basie
• "Scarface" John Williams (1938–1972), singer

Physicians

• John Williams (gastroenterologist), British clinical academic researcher
• Sir John Williams, 1st Baronet, of the City of London (1840–1926), physician to Queen Victoria
• John Ralston Williams (1874–1965), Canadian-American physician
• John Whitridge Williams (1866–1931), obstetrician at Johns Hopkins Hospital

Politicians

Scholars

• John Williams (Ab Ithel) (1811–1862), Welsh antiquary and Anglican priest
• John Williams (art historian) (1928–2015), University of Pittsburgh
• John Williams (bishop of Connecticut) (1817–1899), American bishop of Connecticut, presiding bishop of the Episcopal Church, and dean of Berkeley Divinity School
• John Williams (gastroenterologist), British clinical academic researcher
• John Williams (Oxford academic) (died 1613), British Anglican dean of Bangor, principal of Jesus College, Oxford, and vice-chancellor of the University of Oxford
• John Williams (priest, born 1792) (1792–1858), Welsh Anglican archdeacon of Cardigan, scholar, and schoolmaster
• John Williams (water scientist), member of the Wentworth Group of Concerned Scientists
• John Williams Jr. (university president), former and 12th president of Muhlenberg College
• John Allen Williams (born 1945), American political scientist
• John Beaumont Williams (1932–2005), Australian botanist
• John Burr Williams (1900–1989), early finance theorist; author of The Theory of Investment Value (1938)
• John Davis Williams (1902–1983), chancellor of the University of Mississippi, 1946–1968
• John Ffowcs Williams (1935–2020), professor of engineering at the University of Cambridge, former Master of Emmanuel College
• John Harry Williams (1908–1966), Canadian-American physicist
• John Henry Williams (economist) (1887–1980), American economist
• John Tudno Williams (born 1938), moderator of the Presbyterian Church of Wales and principal of United Theological College, Aberystwyth

Sportsmen

Writers

• John Williams (author, born 1961), Welsh novelist
• John Williams (satirist) (1761–1818), English poet, satirist, and journalist
• John A. Williams (1925–2015), American novelist
• Sir John Bickerton Williams, English nonconformist author and lawyer
• John Edward Williams (1922–1994), American author, editor and professor, known for novels Augustus Bucther's Crossing and Stoner
• John Ellis Williams (1924–2008), Welsh novelist
• John Francon Williams (1854–1911), Welsh journalist, writer, geographer, historian, cartographer and inventor
• John Hartley Williams (1942–2014), English poet
• John James Williams (poet) (1869–1954), Welsh poet
• John Williams Ntwali (1979–2023), Rwandan journalist
• John Richard Williams (poet) (1867–1924), Welsh poet, also known as J. R. Tryfanwy
• John Sibley Williams (born 1978), American poet and fiction writer

Others

• Sir John Williams (shipbuilder) (1700–1784) ship designer to the Royal Navy
• John Williams, engineer of the Montgomery Canal
• John Williams (actor) (1903–1983), English stage, film, and television actor
• John Williams (barrister) (1757–1810), Welsh barrister and legal writer
• John Williams (radio personality) (born 1959), American radio personality
• John Williams (goldsmith), Welsh-born goldsmith based in London
• John Constantine Williams Sr. (died 1892), cofounder of St. Petersburg, Florida
• John Eddie Williams, American attorney
• John G. Williams (ornithologist) (1913–1997), Welsh ornithologist
• John H. Williams (film producer) (born 1953), film producer
• Grant Williams (actor) (John Joseph Williams, 1931–1985), American actor
• J. Lloyd Williams (1854–1945), botanist, author, and musician
• John T. Williams (woodcarver) (1960–2010), Native American woodcarver and shooting victim
• John W. Williams (legislative clerk) (1869–1934), American lawyer, clerk of the Virginia House of Delegates