John Hennessy
John Hennessy is the name of the following people:
- John Hennessy (Archbishop) (1825-1900), Irish-American clergyman, Archbishop of Dubuque
- John Joseph Hennessy (1847–1920), Irish clergyman, Bishop of Wichita
- John L. Hennessy (* 1952), American computer scientist, President of Stanford University
- John Pope-Hennessy (1913–1994), British art historian and director of the British Museum in London