John Hennessy was a 19th-century Irish-born prelate of the Roman Catholic Church in the United States. He served as bishop and then as the first archbishop of the Archdiocese of Dubuque in Iowa from 1866 to 1900.
- Occupation
- Catholic priest, Catholic bishop
- Position held
- Roman Catholic Archbishop of Dubuque, Roman Catholic Bishop of Dubuque
- Born
- August 20, 1825
- Died
- March 4, 1900
