Michael Cusack (Irish: Mícheál Ó Ciosóg) (1847 - 1906) was an Irish teacher and founder of the Gaelic Athletic Association.

He was born in the parish of Carron on the eastern fringe of the Burren, County Clare, in 1847 during the famine. Cusack became a teacher. He traveled throughout Ireland teaching in Enniscorthy, St Colman's College, Corofin, Lough Cutra, Newry, Blackrock College, Clongowes Wood and Kilkenny College before eventually settling in Dublin. He opened the Civil Service Academy on Gardiner St. in Dublin, which trained young men for entrance exams for Trinity College, Dublin, medical and law schools & for entry into the navy, army and constabulary.

Together with Maurice Davin, of Carrick-on-Suir, County Tipperary, he called a meeting in Hayes’s Commercial Hotel, Thurles, County Tipperary, on 1 November 1884, and founded the Gaelic Athletic Association (GAA).

Davin was elected president and Cusack became its first secretary. Later, Archbishop Thomas William Croke (May 28 1824 - July 22 1902), Archbishop of Cashel & Emly, Michael Davitt and Charles Stewart Parnell became patrons. Cusack also became involved in the Irish language movement, founding The Celtic Times, a weekly newspaper which focused on 'native games' and Irish culture.

Cusack, also known as "Citizen Cusack" has been identified as the model for the bigoted nationalist character "The citizen" in the "Cyclops" episode of James Joyce's Ulysses. In a draft of the chapter the citizen is repeatedly called "Cusack."

Cusack died on 27 November 1906 at the age of 59. The newly opened Michael Cusack Visitor Centre located on the original homestead in Carron, The Burren, Co. Clare is dedicated to recounting the fascinating story of Michael Cusack and the idealism which led to him founding the Gaelic Athletic Association. The Clare GAA pitch in Ennis is named "Cusack Park" in his honour as is the "Cusack Stand" in Croke Park, Dublin.

The primary school Gaelscoil Mhíchíl Cíosóg in Ennis, Co.Clare, is also named after him.

Michael Cusack (born 1984-07-11 in Doncaster) is a rugby union footballer for Leeds Tykes . His usual position is at prop.