The Irish Republican Brotherhood (IRB; ) 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 organised by John O'Mahony and became known as the Fenian Brotherhood (later 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.