Hennessy (or Hennessey) is an Irish surname, being the anglicised form of Ó hAonghusa.

Notable people with the surname include:

• Arthur Hennessy (1876–1959), Australian pioneer rugby league identity
• Bill Hennessy (disambiguation)
• Carly Smithson (née Hennessy, born 1983), Irish singer
• Christie Hennessy (1945-2007), Irish singer
• Claire Hennessy (born 1986), Irish novelist
• Clinton Hennessy (born 1977), Irish sportsperson
• David Hennessy (1858–1890), police chief of New Orleans
• Esmé Frances Hennessy (born 1933), South African botanist
• George Hennessy, 1st Baron Windlesham (1877, 1953), British soldier and Conservative politician
• Jean Hennessy (1874–1944), French politician and member of the Hennessy family
• Jacqueline Hennessy (born 1968), journalist
• Jill Hennessy (born 1968), film and television actress
• Joe Hennessy (born 1956), former Irish sportsperson
• Archbishop John Hennessy (1825–1900), head of the Roman Catholic Archdiocese of Dubuque
• John L. Hennessy (born 1953), American computer scientist and current president of Stanford University
• John Pope Hennessy (1834–1891), Irish colonial administrator and politician - eighth governor of Hong Kong, fifteenth governor of Mauritius, MP for King's County
• Josh Hennessy (born 1985), professional ice hockey player
• Kevin Hennessy (born 1961), Irish retired sportsperson
• Larry Hennessy (1929–2008), American basketball player
• Matt Hennessy (born 1997), American football player
• Matthew Hennessy, Irish computer scientist
• Neil Hennessy (born 1978), musician and music producer/engineer
• Patrick Hennessy, several people including
  • Patrick Hennessy (painter), (1915–1980), an Irish artist
  • Sir Patrick Hennessy (industrialist), (1898–1981), an Irish-born British industrialist,
• Peter Hennessy (born 1947), English historian of government
• Ryan Hennessy (born 1995), Irish singer and musician
• Séamus Hennessy (hurler, born 1989), Irish sportsperson
• Swan Hennessy (1866–1929), Irish-American composer resident in Paris
• Thomas Hennessy (politician), Irish politician
• Thomas Hennessy (American football) (born 1994), American football player
• W. Louis Hennessy (born 1955), 4th Circuit Court Associate Judge in Maryland, former Maryland Delegate
• William Hennessy (disambiguation)

• Hennessey (surname)

Surname list

This page lists people with the surname Hennessy.
If an internal link intending to refer to a specific person led you to this page, you may wish to change that link by adding the person's given name(s) to the link.