Bryan Cusack (2 August 1881 – 24 May 1973) was an Irish Sinn Féin politician and medical doctor.

[1] In January 1919, Sinn Féin MPs who had been elected in the Westminster elections of 1918 refused to recognise the Parliament of the United Kingdom and instead assembled at the Mansion House in Dublin as a revolutionary parliament called Dáil Éireann, though Cusack did not attend as he was in prison.

[2] He re-elected unopposed as a Sinn Féin Teachta Dála (TD) for the Galway constituency at the 1921 general election.

He was re-elected as an anti-Treaty Sinn Féin TD for Galway at the 1922 general election but did not take his seat in Dáil Éireann.

He became a founder member of Fianna Fáil in 1926 and stood unsuccessfully for the party in Galway at the June 1927 general election.