William Kennedy may refer to:

Politics and law

William Kennedy (North Carolina politician) (1768–1834), U.S. Congressman from North Carolina
William Kennedy (New Jersey politician) (1775–1826), American politician, acting governor of New Jersey
William Kennedy (Montana politician) (1835–1904), miner, restaurant and hotel proprietor, 8th mayor of Missoula, Montana
William Kennedy (Wisconsin politician) (1841–1910), American lawyer and legislator
William Kennedy (Connecticut politician) (1854–1918), United States congressman from Connecticut
William Nassau Kennedy (1839–1885), Manitoba politician, mayor of Winnipeg
William James Kennedy (politician) (1857–1912), Manitoba politician
William Walker Kennedy (1882–1963), Manitoba politician and lawyer
William Farris Kennedy (1888–1951), British Columbia politician
William Costello Kennedy (1868–1923), Canadian businessman and politician
William Rann Kennedy (1846–1915), British jurist and Lord Justice of Appeal, classical scholar
William Francis Kennedy (died 1874), member of the Queensland Legislative Assembly
William H. Kennedy III (active since 1993), American lawyer and associate counsel to president Clinton

Arts and entertainment

William Kennedy (author) (born 1928), American Pulitzer-winning novelist
William Stetson Kennedy (1916–2011), American author and civil rights activist
William Kennedy (poet) (1799–1871), Scottish poet, journalist, and diplomat
William Kennedy (painter) (1859–1918), Scottish painter
William Denholm Kennedy (1813–1865), Scottish historical, genre and landscape painter
William Kennedy (drummer), drummer for Yellowjackets

William Kennedy (explorer) (1814–1890), Canadian sailor and searcher for John Franklin
William Kennedy (Royal Navy officer) (1838–1916), British admiral
William Clark-Kennedy (1879–1961), Canadian serviceman and recipient of the Victoria Cross
William Quarrier Kennedy (1903–1979), British geologist
William James Kennedy (active since 1990), British geologist
William Kennedy Smith (born 1960), American physician and member of the Kennedy family
William John Kennedy (1919–2005), activist for the rights of Australian Aborigines
William Parker Kennedy (1892–1968), president of the Brotherhood of Railroad Trainmen (BRT) from 1949 to 1962
William Kennedy (Scottish footballer) (fl. 1890s)
William Kennedy (footballer, born 1890) (1890–1915), English footballer
William Kennedy (coach), Scottish footballer
William Kennedy (athlete) (1898–?), Canadian Olympic athlete
William Kennedy (cricketer) (1853-1889), New Zealand cricketer
William Kennedy (rugby league, born 1969), Australian rugby league player
William Kennedy (rugby league, born 1997), Australian rugby league player
William Kennedy (priest) (died 1940), Anglican priest in Ireland
W. P. M. Kennedy (William Paul McClure Kennedy, 1879–1963), Canadian historian and legal scholar