John W. Hennessey Jr. (born March 25, 1925, Danville, Pennsylvania) is an American academic and educator. He has spent most of his life in academia, as professor, dean, and provost. He is Third Century Professor Emeritus at Dartmouth College, where he served for eight years as dean of the Tuck School of Business, during formative years at Tuck. After retirement from teaching applied and professional ethics, he became the provost of the University of Vermont, later serving as interim president. He has served on more than thirty boards of nonprofit and corporate entities, often as chair.
His first wife, Jean Lande Hennessey, was an international environmental commissioner and academic program manager, and she was a leading New Hampshire Democratic strategist and activist. She died in June 2004.
In February 2006, he married Madeleine May Kunin, former Governor of Vermont, Ambassador to Switzerland, professor and public commentator on issues of social justice and the environment. The couple now live in Burlington, Vermont on Lake Champlain.