Billy is a given name and a common nickname for William. Notable people with the name include:
- Billy the Kid (1859–1881), American Old West gunfighter born Henry McCarty, also known as William H. Bonney
- Billy Baldwin (decorator) (1903–1983), American interior decorator
- Billy Baldwin (baseball) (1951–2011), American Major League Baseball outfielder
- Billy Barnes (disambiguation)
- Billy Bevan (1887–1957), Australian actor
- Billy Bland (singer) (1932–2017), American R&B singer and songwriter
- Billy Boyd (disambiguation)
- Billy Blue (c. 1767 – 1834), African-American convict transported to Australia
- Billy Brewer (footballer) (died 1914), English professional footballer
- Billy Brown (disambiguation)
- Billy Burke (disambiguation)
- Billy Butler (singer) (1945–2015), American soul singer and songwriter
- Billy Cesare (born 1955), American football player
- Billy Connolly (born 1942), Scottish comedian
- Billy Corgan (born 1967), American musician, frontman of Smashing Pumpkins
- Billy Crawford (born 1982), Filipino-American actor and television personality
- Billy Crook (English footballer) (1926–2011)
- Billy Crook (American soccer) (born 1964)
- Billy Crystal (born 1948), American actor
- Billy Davis (disambiguation)
- Billy De Wolfe (1907–1974), American actor
- Billy Edwards Jr., American college football player
- Billy Eppler (born 1975), American baseball executive
- Billy Fox (politician) (1939–1974), Irish politician
- Billy Fox (boxer) (1926–1986), American light-heavyweight boxer
- Billy Forbes (Scottish footballer) (fl. 1911–1926)
- Billy Forbes (footballer, born 1990), Turks and Caicos Islands footballer
- Billy Gallagher (chef) (1948–2016), South African chef and businessman
- Billy Gibbons (born 1949), American musician
- Billy Gilmour (born 2001), Scottish footballer
- Billy Graham (1918–2018), American evangelist
- Billy Hahn (1953–2023), American basketball coach
- Billy Howard, English comedian
- Billy Howard (gridiron football) (1950–2005), American football player
- Billy Howerdel (born 1970), American musician, founding member of A Perfect Circle, frontman of ASHES dIVIDE
- Billy Herrington (1969–2018), American actor
- Billy Idol (born 1955), English rock musician
- Billy Joel (born 1949), American musician
- Billy Johnson (disambiguation)
- Billy Jones (disambiguation)
- ABilly S. Jones-Hennin (born 1942), American LGBT rights activist
- Billy Kametz (1987–2022), American voice actor
- Billy Knight (born 1952), American basketball player and executive
- Billy Knight (basketball, born 1979) (1979–2018), American basketball player
- Billy Knight (tennis) (born 1935), British tennis player
- Billy Magnussen (born 1985), American actor
- Billy Martin (1928–1989), American baseball player and manager
- Billy Masters (columnist) (born 1969), American gossip columnist
- Billy Masters (American football) (born 1944), former American Football League and National Football League player
- Billy Rush Masters (1950–1981), American composer and rock guitarist
- Billy Mays (1958–2009), American television salesperson
- Billy Mays (footballer) (1902–1959), Welsh footballer
- Billy McShepard (born 1987), American basketball player in the Israeli National League
- Billy Meier (born 1937), claims to be in regular contact with extraterrestrial beings
- Billy Mitchell (gamer) (born 1965), American gamer and restaurateur
- Billy Murray (disambiguation)
- Billy Name (1940–2016), American lighting designer
- Billy Ouattara (born 1992), Ghanaian/French basketball player
- Billy Parker (disambiguation)
- Billy Parks (1948–2009), American football player
- Billy Payne (born 1947), American golf administrator
- Billy Price (actor) (born 2000), English actor
- Billy Price (American football) (born 1995), American football player
- Billy Reid (fashion designer) (born 1964)
- Billy Rose (1899–1966), American impresario and husband of Fanny Brice
- Billy Joe Royal (1942–2015), American singer
- Billy Santoro (born 1975 or 1976), American gay pornographic film actor
- Billy Sharp (born 1986), English footballer
- Billy Sheehan (born 1953), American bass player
- Billy (slave), an African-American slave accused of treason
- Billy Smart Jr. (1934–2005), British circus performer and impresario
- Billy Snedden (1926–1987), Australian politician
- Billy Tauzin (born 1943), American lobbyist and politician
- Billy Taylor (disambiguation)
- Billy Unger (born 1995), American actor
- Billy Wade (cricketer) (1914–2003), South African cricketer
- Billy Wade (racing driver) (1930–1965), American race car driver
- Billy West (born 1952), American voice actor
- Billy Walker (disambiguation)
- Billy Williams (disambiguation)
- Billy Wright (disambiguation)
- Billy Zane (born 1966), American actor
- Reverend Billy, of Reverend Billy and the Church of Stop Shopping, New York City-based performance group