Drawing on a synthesis of I. A. Isaev’s works, the author examines the universal features of political fictions and applies these insights to the analysis of medieval state formation, focusing on the Portuguese case of the 11th century. State formation (etatogenesis), understood as a process marked by the tension between the rational and the utopian, is saturated with the politicization of the fictive. Studying etatogenesis in the context of the Reconquista and its frontier dynamics reveals historical referents for the generation of political fictions at the initial stage of Portuguese state formation. The separation from León — first as a county, then as a polity that acquires de facto kingdom status — is largely attributable to the military and political talent of Afonso Henriques. Exploiting maturing objective conditions, he led a separatist movement and demonstrated the capacity to construct political fictions that helped secure and sustain independence from León and Castile and to establish a viable state. The analysis of political fictions in 11th-century Portugal opens new avenues for the study of etatogenesis.