Thomas James Clarke was an Irish republican and a leader of the Irish Republican Brotherhood. Clarke was arguably the person most responsible for the 1916 Easter Rising. A proponent of armed struggle against British rule in Ireland for most of his life, Clarke spent 15 years in English prisons prior to his role in the Easter Rising, and was executed by firing squad after it was defeated.

The Irish Republican Brotherhood was a secret oath-bound fraternal organisation dedicated to the establishment of an "independent democratic republic" in Ireland between 1858 and 1924. Its counterpart in the United States of America was initially the Fenian Brotherhood, but from the 1870s it was Clan na Gael. The members of both wings of the movement are often referred to as "Fenians". The IRB played an important role in the history of Ireland, as the chief advocate of republicanism during the campaign for Ireland's independence from the United Kingdom, successor to movements such as the United Irishmen of the 1790s and the Young Irelanders of the 1840s.