William Hennessy
William Hennessy may refer to:

William Hennessy (violinist), Australian classical violinist
William Hennessy (wrestler), American wrestler
William C. Hennessy, American civil servant and political figure
William John Hennessy, Irish artist
William Maunsell Hennessy, Irish official and scholar
Bill Hennessy (Cork hurler) (1882–1954)
Bill Hennessy (Kilkenny hurler) (born 1968)