Although most Catholics already regarded Hildegard as a saint, canonization attempts in the past had gone wrong for various reasons, Italy's ANSA news agency reported.
In recent years, the nun has been the subject of sermons by the pope, particularly amidst sex abuse scandals. Benedict has said Hildegard was a model for the way Catholics should react today.
Hildegard, who lived from 1098 to 1179, was a writer, composer, philosopher, the head of an abbey of nuns and visionary who founded the monasteries of Rupertsberg and Eibingen. She wrote theological, botanical and medicinal texts, as well as letters, liturgical songs and poems.