William, Willie, Will, Billy or Bill Griffin may refer to:
Arts and entertainment
William Griffin (painter) (1811–1870), New Zealand painter
Billy Griffin (born 1950), American singer-songwriter
Rakim (William Michael Griffin Jr., born 1968), American rapper
Bill Griffin (musician), American mandolinist and luthier
Religion
William Richard Griffin (1882–1944), American Roman Catholic bishop
William A. Griffin (Roman Catholic bishop) (1885–1950), American Roman Catholic Bishop of Trenton
William A. Griffin (Christian churches and churches of Christ) (fl. 1980s–2000s), Christian preacher and President of Mid-Atlantic Christian University
Sports
Willie Griffin (1922–1983), Irish hurler
Billy Griffin (footballer) (born 1940), English footballer, see List of Sheffield Wednesday F.C. players
William Griffin (rugby) (fl. 1950s), Welsh rugby union and rugby league footballer
Others
William Henry Griffin (1812–1900), Canadian civil servant
William D. Griffin (1936–2011), American historian, author, and educator
William Griffin (geologist), recipient of the Clarke Medal for 2013 in the field of geology