William Wynn or William Wynne may refer to:

• William Wynne (historian) (c. 1671–1704), priest and historian
• William Wynne (MP for Caernarvon), (1678–1754), MP for Caernarvon, 1749-1754
• William Wynne (lawyer) (c. 1692–1765), lawyer and writer
• William Wynn (poet) (c. 1709–1760), Welsh priest and poet
• William Wynne (judge) (1729–1815), English lawyer, Dean of Arches and Master of Trinity Hall, Cambridge
• William Wynne (Irish politician) (c 1764–1855), Irish politician, MP for Sligo Borough 1799–1800
• William Watkin Edward Wynne (1801–1880), MP for Merionethshire (1852–1865) and antiquarian
• William J. Wynn (1860–1935), Member of the US House of Representatives from California
• William Andrew Wynne (1869–1951), baseball pitcher, played one Major League game for the Washington Senators
• William Wynn (footballer) (1876–1944), Shrewsbury Town F.C. and Wales international footballer
• William Robert Maurice Wynne (died 1909), MP for Merionethshire 1865–1868
• Will Wynn (American football) (born 1949), defensive end for the Philadelphia Eagles and the Washington Redskins
• Will Wynn (born 1961), Mayor of Austin, Texas
• William Wynne (athlete) (born 1990), American hurdler
• William H. Wynn, trade unionist and first president of the United Food and Commercial Workers International Union
• Bill Wynne, American author and dog trainer