John J. Brennan (1901 – 6 August 1977)[1] was a draper and publican, Fianna Fáil politician and a member of Seanad Éireann from 1960 to 1977.

[2] In Castleblayney, he was chair of the urban district council and president of the chamber of commerce.

[2] He stood unsuccessfully for Dáil Éireann in Monaghan in the elections of 1948,[2][3] 1954,[2][3] and 1957.

[3] He was a friend and early political backer of Erskine H. Childers, Monaghan TD and later President of Ireland.

[2] He was elected to the 9th Seanad on 9 February 1960 at a by-election to the Administrative Panel[1] caused by the death of John O'Leary.