|Assumed office |
|Dublin City Council|
18 February 1987
|Political party||Social Democrats (since 2015)|
|Independent (Before 2015)|
|Alma mater||Trinity College Dublin|
Gannon was born in Dublin’s North Inner City. The son of a street trader he left school to train as a plumber. When he was unemployed he completed a one-year TAP foundation course for higher education. He went on to study History and Politics at Trinity College Dublin. 
Gannon was elected to Dublin City Council in 2014 in the North Inner City electoral area as an independent candidate.
In September 2015 he joined the newly formed Social Democrats Party. Gannon was one of five general election candidates put forward by the Social Democrats to contest the 2016 General Election. He ran in the Dublin Central Constituency. Gannon lost out on a seat to Maureen O’Sullivan by a tight margin in a competitive constituency which included Mary Lou McDonald and Paschal O’Donohoe. 
Gannon is active in the Irish media. He often speaks about access to education, more recently how the lack of access to education plays into poverty and gang violence. He has also spoken extensively about the Magdalene laundries and the need to preserve the historical significance of the sites - particularly the last laundry to close in Ireland, located in Gloucester Street, Dublin 1. 
- "Gary Gannon - MacGill Summer School". MacGill Summer School. 1 June 2016.
- "'You grow up in a flat complex in Summerhill and you think the State is out to get you'". The Irish Times.
- "'I was the only one judging people'". The Irish Times.
- "The Irish Times, Local Election Results for Dublin City Council". The Irish Times.
- "Social Democrats name five general election hopefuls". Irish Examiner. 6 September 2015.
- "Dublin Central results: Maureen O'Sullivan retains seat in tight contest". The Irish Times.
- "At Lunch With… Councillor Gary Gannon". Dublin Inquirer. 14 July 2015.
- "Hutch-Kinahan feud may end but the cycle of violence will not". The Irish Times.
- Gannon, Gary. "Magdalene memorial: 'I grew up in the shadow of that laundry'".
- O’Loughlin, Ed (21 March 2018). "A Blot on Ireland's Past, Facing Demolition" – via NYTimes.com.