Michael or Mike Hennessy or Hennessy may refer to:
Michael Hennessey (born c. 1948), American attorney and former Sheriff of San Francisco Mike Hennessey (1928–2017), English music journalist and jazz pianist Michael Hennessy (fl. 1920s–1930s), Irish politician and businessman Mike Hennessy (fl. 1990s–2000s), British rower, Michael "Mickey" Hennessy (1915—1991), Canadian boxer and politician