John O'Connor Power was an Irish Fenian and a Home Rule League and Irish Parliamentary Party politician and as MP in the House of Commons of the United Kingdom of Great Britain and Ireland represented Mayo from June 1874 to 1885. From 1881, he practised as a barrister specialising in criminal law and campaigning for penal reform.

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.