Bill Gannon (23 June 1902 – 12 September 1965) was a well-known militant of the Irish Republican Army (IRA) and later a leading member of the Communist Party of Ireland.

[1] O'Higgins was especially hated by IRA members for having ordered the executions of seventy-seven of their fellows during the Civil War, an act for which he outspokenly took responsibility and refused to express any remorse.

On 8 December 1922 O'Higgins signed off on the retaliatory executions of four senior republicans (Liam Mellows, Richard Barrett, Joe McKelvey and Rory O'Connor) for the killing of a member of Dáil Éireann.

Gannon and Doyle benefited from the amnesty for IRA members issued by Éamon de Valera on his accession to power in 1932, and after that date they could openly admit their part in assassinating O'Higgins without fear of being prosecuted.

Gannon is at present mainly remembered for his major part in organising Irish volunteers (the Connolly Column) to fight on the Republican side in the Spanish Civil War, a work undertaken in close co-operation with Frank Ryan and Peadar O'Donnell,[4] and which came to overshadow his earlier fame (or notoriety) in connection with the O'Higgins assassination.