William Hennessy

William Hennessy may refer to:

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