This introductory chapter sets the stage for a comprehensive diachronic study of Ireland’s evolving relationship with its diaspora, focusing particularly on the role of Irish-American business elites in shaping the island’s economic trajectory since independence in 1922. While the economic transformation of Ireland has been widely studied, this book draws attention to an often-overlooked factor: the influence of diaspora figures in attracting foreign direct investment and shaping public policy. Moving beyond synchronic approaches, the introduction outlines the book’s ambition to analyse this relationship over nearly a century, examining how Ireland—and more modestly Northern Ireland—strategically engaged its diaspora to support economic development. The chapter presents the theoretical framework, key research questions, and sources, including archival materials, parliamentary debates, press coverage, and interviews. It explores both the opportunities and tensions inherent in diaspora engagement, especially when informal influence challenges national sovereignty. By investigating the complex and sometimes contradictory motivations—financial as well as emotional, cultural, and social—that drive diaspora involvement, the book argues for a nuanced understanding of how national and transnational logics intersect. Ultimately, this introduction positions the diaspora not as a passive legacy of emigration, but as an active and strategic actor in the political economy and economic development of the two Irelands.