Collins was born near Sam's Cross, Clonakilty, Co Cork, on 16 October 1890. He became a post office clerk in 1906. Sent to London, he learned Irish at Gaelic League classes and joined Sinn Féin. He later joined both the Irish Republican Brotherhood and the Irish Volunteers before returning to Ireland in January l916, to avoid conscription in England.

During the Easter Rising, Collins fought in the General Post Office. In December 1916, he was released from internment and became a member of the IRB supreme council. When Eamon de Valera and other republicans were arrested in 1918, Collins eluded the police and began to build up a remarkable intelligence system. Elected MP for South Cork in 1918, 'the Big Fellow' became home minister in the First Dáil, but missed its opening; he was preparing de Valera's escape from Lincoln jail. He later became president of the IRB's supreme council.

In the ensuing guerrilla warfare, Collins' special squad systematically assassinated members of the 'G' division of the Dublin police, Dublin Castle's main source of intelligence; he had his own informants at detective headquarters. On 'Bloody Sunday', 21 November 1920, his men shot dead eleven British intelligence officers. In retaliation, British Black and Tans killed fourteen people at a football game. Collins' family home in Cork was burned out in April 1921.

A reluctant negotiator and signatory of the 1921 Anglo Irish Treaty, Collins wrote 'early this morning I signed my death warrant'. He became chairman of the provisional government which preceded the Irish Free State, and Dublin Castle was surrendered to him. On the outbreak of the Civil War in June 1922, he took command of the forces loyal to the government.

On 22 August 1922, ten days after the death of Arthur Griffith he was ambushed and shot dead at Béal na mBláth, Co Cork.

Memorials at Sam's Cross (4 1/4 miles/ 7 km WSW of Clonakilty); at Béal na mBláth (2 miles/3 km SW of Crookstown, Co Cork); and at Leinster Lawn, Merrion Square, Dublin.