This book examines the often contentious world of early 20th-century European nationalism, focusing on the ideologies and movements of Action Française and Integralismo Lusitano. It explores how these movements emerged as reactions against the perceived failures of democracy, particularly in the wake of significant national crises such as France's defeat in the Franco-Prussian War and Portugal's colonial setbacks. At the heart of the analysis is Charles Maurras, the leader of Action Française, who advocated for a return to monarchism, authoritarianism and traditional values as a remedy for France's moral and political decline. The book also examines Integralismo Lusitano, a movement that drew inspiration from Maurras' ideas and adapted them to the specific context of Portugal. The book provides a detailed comparison of these two movements, offering a nuanced exploration that will appeal to scholars of European history, political theory and the rise of authoritarian movements in the early 20th century.