A bold new exploration of Fenian revolutionary activity across the Americas In the aftermath of the American Civil War, the Fenian movement stood at a crossroads. Thousands of demobilized Irish soldiers held the power to reshape history. Inspired by a popular desire to expel monarchical and aristocratic influence from the New World, many American Fenians began to align their efforts to establish an independent Irish Republic with the wider aims of American republican expansion. In doing so, the Fenians' fight for Irish liberation became more than a single cause - it was a web of alliances, contradictions, and ambitions, carried out under a common banner of republicanism. In The Fenian Empire, Patrick J. Mahoney uncovers the untold story of how Fenianism intersected with race, colonialism, and internationalist solidarity across North America and the Caribbean at a time of intense political turmoil. Fueled by the cause of republican expansion, the period saw the unlikely emergence of Black Fenian volunteers, attempts to land Fenian troops into Mexico and Cuba, and the participation of many Fenians in the subjugation of Native peoples along the western plains of North America. While their views and strategies varied, their aim remained clear: Irish freedom. Drawing on an expansive range of archives and sources across multiple languages, Mahoney delivers a fresh take on the Fenian story, guiding readers through a world of clandestine meetings, personal networks, propaganda, and long-forgotten military operations. What results is a groundbreaking look at how one struggle echoed across the revolutionary landscape of the Civil War era.