William, Will, Bill, or Billy Davies may refer to:
Arts and literature
William Davies (actor) (1751–1809), English actor
William Davies (died 1819), English publisher with Cadell & Davies
William Edmund Davies (1819–1879), English bookmaker
W. H. Davies (William Henry Davies, 1871–1940), Welsh poet
William Davies (screenwriter) (fl. 1980s–2010s), British-born American screenwriter
Law and politics
William Davies (Georgia judge) (1775–1829), Georgia-based politician and lawyer
William Davies (Pembrokeshire MP) (1821–1895), British member of parliament (MP) for Pembrokeshire, 1880–1892
William Davies (New South Wales politician) (1824–1890)
William T. Davies (1831–1912), lieutenant governor of Pennsylvania, United States, 1887–1891
Sir William Howell Davies (politician) (1851–1932), British MP for Bristol South, 1906–1922
William Thomas Frederick Davies (1860–1947), South African surgeon, army officer and politician
William Rees-Davies (judge) (William Rees Morgan Davies, 1863–1939), British MP for Pembrokeshire, 1892–1898
Rupert Davies (politician) (William Rupert Davies, 1879–1967), Canadian author, newspaper publisher and senator
Billy Davies (politician) (1884–1956), Welsh-born Australian member of the New South Wales Legislative Assembly and the Australian Parliament
Sir William Arthian Davies (1901–1979), British lawyer and judge
William Gwynne Davies (1916–1999), trade unionist and politician in Saskatchewan, Canada
William H. Davies (1931–2017), justice of the Supreme Court of British Columbia
Military
William Davies (Virginia) (fl. 1770s), Continental Army officer in the American Revolutionary War
William Davies (fl. late 18th century), British bullet-mould maker, founder of arms manufacturer Webley & Scott
William W. Davies (USMC) (1900–1985), United States Marine Corps general
Religion
William Davies (priest) (died 1593), Welsh Roman Catholic priest and martyr
William W. Davies (1833–1906), leader of a schismatic Latter Day Saint group in Washington, United States
William David Davies (1897–1969), Welsh Presbyterian minister and theologian
Science and medicine
William Davies (palaeontologist) (1814–1891), British palaeontologist
William Broughton Davies (1831–1906), Sierra Leonean medical doctor
William Edward Davies (1917–1990), American geologist and caver
William Davies (psychologist) (born 1950), British psychologist
Sportspeople
Association football (soccer)
William Davies (footballer, born 1854) (1854–1916), Oswestry F.C. and Wales international footballer
William Davies (footballer, born 1873) (1873–1929), English footballer for Bolton Wanderers
William Davies (footballer, born 1882) (1882–1966), Wrexham F.C., Blackburn Rovers F.C. and Wales international footballer
Billy Davies (Welsh footballer) (1883–1960), Crystal Palace F.C., West Bromwich Albion F.C. and Wales international footballer
William Davies (footballer, born 1884) (1884–1954), footballer for Stoke
Willie Davies (footballer) (1900–1953), Swansea Town F.C., Cardiff City F.C., Notts County F.C.,Tottenham Hotspur F.C. and Wales international footballer
Taffy Davies (William Davies, 1910–1995), Welsh footballer with Watford
Dai Davies (footballer, born 1948) (William David Davies, 1948–2021), Welsh goalkeeper
Billy Davies (born 1964), Scottish footballer and manager
Will Davies (footballer), English footballer
Cricket
William Davies (English cricketer) (fl. 1844)
William Davies (cricketer, born 1825) (1825–1868), English cricketer and clergyman
Bill Davies (cricketer, born 1901) (1901–?), Welsh cricketer
Bill Davies (cricketer, born 1906) (1906–1971), Welsh cricketer
Billy Davies (cricketer, born 1936) (1936–2022), Welsh cricketer
William Davies (cricketer, born 1972), English cricketer
Rugby
William Davies (rugby) (1890–1967), Welsh rugby union and rugby league footballer of the 1910s and 1920s
Will Davies (rugby) (fl. 1910s), rugby league footballer for Great Britain, Wales and Halifax
Will Davies (rugby union) (1906–1975), Wales international rugby union player
Billy Davies (Welsh rugby) (William H. J. Davies, fl. 1930s), rugby union and rugby league footballer
Willie Davies (rugby) (1916–2002), Welsh dual-code rugby footballer
Bill Davies (rugby league) (fl. 1940s), rugby league footballer for Wales, and Huddersfield
Tony Davies (William Anthony Davies, 1939–2008), New Zealand rugby union footballer