Michael Joseph Hennessy was an Irish politician and businessman. He was first elected to Dáil Éireann as an Businessmen's Party Teachta Dála (TD) for Cork East and North East at the 1922 general election. He was elected as a Cumann na nGaedheal TD for Cork East at the 1923, June 1927 and September 1927 general elections. He lost his seat at the 1932 general election.
Hennessy lived at 11 Rahilly Street, Cobh (formerly King Street). In June 1922 the Bishop of Cloyne Robert Browne, contributed £20 each to the election funds of Hennessy and John Dinneen, Commercial and Farmer pro-Treaty candidates respectively for the Cork East and North East constituency.