William Williams may refer to:
Authors and artists
- William Williams (artist) (1727–1791), artist, author of first American novel, Penrose
- William Joseph Williams (1759–1823), his son, artist; painted 3 Presidents
- William Williams (antiquary) (Gwilym Ddu o Arfon) (1739–1817), Welsh historian and poet
- William Williams (Crwys) (1875–1968, bardic name Crwys), Welsh-language poet
- William Williams (Carw Coch) (1808–1872, bardic name Carw Coch), Welsh literary figure
- William Williams (Creuddynfab) (1814–1869), Welsh poet and literary critic
- William Appleman Williams (1921–1990), American historian
- William Carlos Williams (1883–1963), American poet
- Sir William Emrys Williams (1896–1977), British educationalist and editor-in-chief of Penguin Books
- William Williams (surgeon) (1856–1919), Surgeon General
- William T. Williams (born 1942), New York painter
- William Williams Pantycelyn (or, William Williams of Pantycelyn, 1717–1791), Welsh composer of hymns
Military figures
- William Williams (soldier) (?–1814), Soldier killed in defense of Fort McHenry during the War of 1812
- William Williams (VC) (1890–1965), Victoria Cross recipient of the First World War
- William Charles Williams (1880–1915), Victoria Cross recipient of the First World War
- William Williams (Medal of Honor) (1840–?), Medal of Honor recipient of the American Civil War
- Fenwick Williams (Sir William Fenwick Williams, 1st Baronet, 1800–1883), Canadian-born British military leader
- William Reid Williams (1866–1931), United States Assistant Secretary of War
- William Haliday Williams (1845–1916), American Civil War soldier and Medal of Honor recipient
Politicians
- Sir William Williams, 1st Baronet, of Gray's Inn (1634–1700), Welsh lawyer & politician, speaker of the House of Commons
- Sir William Williams, 2nd Baronet, of Gray's Inn (c. 1665–1740), Welsh politician, Member of Parliament (MP) for Denbigh, 1708–1710
- William Peere Williams (1664–1736), MP for Bishop's Castle, 1722–1727
- Sir William Williams, 6th Baronet (c. 1668–1696), Welsh politician
- Sir William Williams, 2nd Baronet, of Clapton (c. 1730–1761), MP for New Shoreham, 1758–1751
- William Williams (Continental Congress) (1731–1811), US Continental Congressman; signed Declaration of Independence for Connecticut
- William Addams Williams (1787–1861), British Member of Parliament for Monmouthshire
- William Williams (Radical politician) (1788–1865), Welsh businessman based in London, Radical MP 1835–1847 and 1850–1865
- William Williams (New York) (1815–1876), US Representative from New York
- William Williams (Indiana) (1821–1896), US Representative from Indiana
- William B. Williams (politician) (1826–1905), US Representative from Michigan
- William Williams (Swansea MP) (1840–1904), British Member of Parliament for Swansea District 1893–1895
- William M. Williams, Jr. (1846–?), member of the Wisconsin State Assembly
- William Williams (Tasmanian politician) (1851–1924), member of the Tasmanian Legislative Council
- William Williams (Australian politician) (1856–1947), member of the New South Wales Legislative Assembly
- William E. Williams (1857–1921), U.S. Representative from Illinois
- W. Llewelyn Williams (1867–1922), Welsh journalist, lawyer and Liberal Party politician
- William R. Williams (1884–1972), US Representative from the state of New York
- William Richard Williams (1895–1963), British civil servant and politician
- Sir Thomas Williams (British politician) (William Thomas Williams, 1915–1986), British Member of Parliament for Warrington
- William M. "Buckskin" Williams, member of the First to Fourth and Sixth Texas Legislatures
- William R. Williams (California politician), California State Treasurer, 1907–1911
Religious figures
- William Williams Pantycelyn (1717–1791), religious leader & musician
- William Williams of Wern (1781–1840), Welsh Independent minister; promoter of the "General Union" movement of 1834
- William Williams (bishop) (1800–1878), bishop of Waiapu in New Zealand
- William Leonard Williams (bishop) (1829–1916), third bishop of Waiapu in New Zealand
- William Williams (priest) (1848–1930), Dean of St David's, 1919–1931
- William Williams (missionary) (1859–1892), Welsh missionary to East Khasi Hills, India
- William Richard Williams (theologian) (1896–1962), theologian and principal of the United Theological College Aberystwyth
- William Williams (Caledfryn) (1801–1869), Welsh Congregational minister, poet and literary critic
Sportsmen
- William Henry Williams (rugby player) (1873–1936), rugby union footballer of the 1900s for Wales, Pontymister RFC, and London Welsh RFC
- William Williams (Halifax RLFC) (20th century), rugby league footballer of the 1900s and 1910s for Wales and Halifax
- William Williams (rugby, born 1866) (1866–1945), rugby union footballer of the 1880s and 1890s for Wales, Cardiff RFC, and London Welsh RFC
- William Williams (rugby, born 1925) (1925–2007), rugby union and rugby league footballer of the 1940s for Wales XV (RU), Monmouthshire, Newport, and Swinton (RL)
- William Williams (footballer) (1856–?), Welsh international footballer of the 1870s and 1880s
- John Williams (footballer, born 1960) (William John Williams), English soccer player
- William M. Williams (1877–1932), head coach of the Clemson college football program in 1897
- J. William Williams (1880–1908), American football player and coach
- Will Williams (born 1992), New Zealand cricketer
Others
- William S. Williams (1787–1849), mountain man and frontiersman
- William Mattieu Williams (1820–1892), English writer on science
- William Williams (academic) (1927–2011), Canadian metallurgical engineer
- William Williams (veterinarian) (1832–1900), Welsh veterinary surgeon
- William Henry Williams (1852–1941), English-born Australian Headmaster and professor
- William Williams (doctor) (1855/6–1911), Welsh doctor and writer on sanitation issues
- William Williams (Commissioner of Ellis Island) (1862–1947), Commissioner of Immigration, Ellis Island
- William Williams (murderer) (1877–1906), last person executed by Minnesota
- William Williams (baseball) (1916–2009), co-owner of the Cincinnati Reds baseball team
- William B. Williams (DJ) (1923–1986), disk jockey on New York City radio station WNEW
- William H. Williams (1910–1999), British production manager and producer
- William W. Williams, author of the Encyclopedia of Pseudoscience
- William Morgan Williams, presenter of a 1969 Frazer Lecture
- William Muir Williams, judge of the Supreme Court of Missouri in 1898
- William M. Williams, IS Commissioner of Internal Revenue 1920–1921
Characters
- "Clean Willy" Williams, a fictional character in Michael Crichton's novel The Great Train Robbery
- William B. Williams, played by John Candy, the babbling, character on Second City Television
- Williams Williams, in The Simpsons episode "Bart the Murderer", the real name of the character Fat Tony
- "William W. Williams", the full name of "Big Billy" from the "Gangreen Gang" in The Powerpuff Girls