Well-studied in historiography, nineteenth-century debates on Portugal's decadence ("decadência") left a deep and long-lasting impression in this country's historical culture. The idea that Portugal had reached its apogee and was inexorably losing ground in the concert of other European peoples led its intellectuals to search in the past for elements capable of inspiring a national rebirth. Among the most sought epochs was the Middle Ages, revalued in the context of romantic culture. This article explores how the concept of national decadence was examined in nineteenth- and twentieth-century Portuguese medievalist discourses.