Through eleven years of marriage with Charlemagne, Hildegard helped share in his rule as well as having nine children with him, including the kings Charles the Younger and Pepin of Italy and the emperor Louis the Pious.

Thegan of Trier, a ninth-century biographer of Hildegard's son Louis emphasizes her Alemannian heritage and descent from duke Gotfrid through her mother, indicating that Imma was of higher status than Gerold.

[10] Charlemagne took Hildegard to the Frankish royal palace at Thionville, where they stayed for two months before he set off on a campaign in Saxony.

[11] At the end of the campaigning season, Charlemagne returned to Thionville, and during this period the couple's son Charles was born.

[13] Charlemagne, heeding the Pope's call for aid, invaded Lombardy in late 773 and besieged the Lombard capital of Pavia.

[16][17] Charlemagne and Hildegard likely went through a ritual installation as the new king and queen in Pavia (though no direct source exists),[18] and a charter issued in Lombardy in July was a grant of Lombard land to the Abbey of St. Martin made in both of their names.

[22] Hildegard was pregnant when they arrived, and gave birth to twin boys, Louis and Lothair, while Charlemagne was on campaign.

[31] Around this time, Hildegard and Charlemagne jointly commissioned the Godescalc Evangelistary, a surviving illuminated manuscript of the Gospels and exemplary piece of Carolingian Renaissance art.

Hildegard was buried at the Abbey of Saint-Arnould at Metz, and Charlemagne arranged for her tomb to be perpetually lit and for daily masses to be said there, as well as commissioning an epitaph in her honor from his courtier Paul the Deacon.