This book is the first definitive history of the Northern Ireland Labour Party (NILP), a unique political force which drew its support from Protestants and Catholics and became electorally viable despite deep-seated ethnic, religious and national divisions. Formed in 1924 and disbanded in 1987, the NILP succeeded in returning several of its members to the locally-based Northern Ireland parliament in 1925-29 and 1958-72 and polled some 100,000 votes in both the 1964 and the 1970 British general elections. As British Labour's 'sister' party in the province from the late 1920s until the late 1970s, the NILP could rely on substantive fraternal and organisational support at critical junctures in its history. Despite its political successes the NILP's significance has been downplayed by historians, partly because of the lack of empirical evidence and partly to reinforce the simplistic view of Northern Ireland as the site of the most protracted sectarian conflict in modern Europe. For the first time this book brings together important archival sources and the oral testimonies of former NILP members to explain the enigma of an extraordinary political party operating in extraordinary circumstances. The book situates the NILP's successes and failures in a broad historical framework, providing the reader with a balanced account of twentieth-century Northern Irish political history. This book will appeal to students and scholars of labour movements, as well as non-specialists who wish to learn more about the NILP's brand of democratic socialism, its ideological and logistical ties to British Labour and the character of its cross-sectarian membership.