William, Will, Willie, Bill, or Billy Harper may refer to:
Arts and entertainment William A. Harper (1873–1910), Canadian-born artist Billy Harper (born 1943), American jazz saxophonist William Claude Harper (born 1944), American jewelry artist William Harper (composer) (born 1949), American composer and photographer William Jackson Harper (born 1980), American actor
Law and politics William Harper (South Carolina politician) (1790–1847), US Senator from South Carolina William Harper (Louisiana politician) (died 1909), American politician in Louisiana William Harper (Rhodesian politician) (1916–2006), Royal Air Force pilot and Rhodesian politician
Sports Association football (soccer) Billy Harper (footballer, born 1877) (1877–1947), English footballer Bill Harper (footballer, born 1897) (1897–1989), Scottish football goalkeeper Billy Harper (footballer, born 1897) (1897–1982), English footballer Bill Harper (footballer, born 1900) (born 1900), Scottish football goalkeeper
Other sports Bill Harper (baseball) (1889–1951), American baseball pitcher Bill Harper (soccer) (fl. 1968), Canadian soccer player Willie Harper (born 1950), American football linebacker
Others William Rainey Harper (1856–1906), American academic, first president of the University of Chicago William Edmund Harper (1878–1940), Canadian astronomer William Harper Jr. (fl. 1910s), American pioneer aviator with the Wright brothers
See also William Harpur (died 1574), merchant and Lord Mayor of London