In this fascinating history of European federalism during the 1920s and 1930s, Rebecca Shriver uncovers a surprising grassroots phenomenon. Moving beyond the familiar story of elite male intellectuals, she reveals how women and feminist activists in the Pan-European Union, the New Europe Group, and the Women's International League for Peace and Freedom shaped new visions for a united Europe. These organizations imagined a continental federation that prioritized cooperation, reconciliation, and individualism-qualities they associated with women's leadership. By reframing the failures of the nation-state as products of 'man-made' systems, they offered alternatives grounded in gendered ideas of peace. Drawing on rich archival research, this study challenges conventional narratives of European integration and demonstrates the central role of women in its intellectual foundations. Both timely and provocative, it speaks to enduring debates on democracy, polarization, and international cooperation that continue to resonate today.