Louis (Abbot of Saint-Denis)(circa 800 – 867) was the illegitimate son of Rotrude, daughter of Charlemagne, and Rorgon I of Maine.

He was elevated, with Lupus Servatus, to the Abbey of Saint-Pierre of Ferrières in the Gâtinais. He became an abbot in 838 and Abbot of Saint-Denis in 840 or 841.

He was the archchancellor first of his uncle Louis the Pious and then of his cousin Charles the Bald. In 844, Charles made him abbot of three foundations: Saint-Denis, Saint-Riquier, and Saint-Wandrille.

In 858, he and his half-brother Joscelin were captured by the Vikings and only liberated with the payment of a large ransom. [http://en.wikipedia.org/wiki/Louis_(Abbot_of_Saint-Denis]