The original settlers of the area around the Tegernsee lake were Illyrians that arrived in the early Stone Age. The history of the current region and of the town began with the arrival of the Bavarians in the 6th century. The noble family of the Agilolfings ruled this region and the entire Duchy of Bavaria.
The Benedictine Abbey of Tegernsee was founded in 746 by the brothers Adalbert and Ottokar, of the noble family of Huosi. The abbey's name derives from Old High German tegarin seo, meaning large lake. Although much of the town's early history is unknown as a result of Magyar incursions in the 10th century, it is known that relics of St. Quirinus, which the abbey's founders obtained from Pope Paul I, were transferred in the 8th century from Rome to Tegernsee to be placed in its first church. The monastery had a substantial influence on the development of Southern Bavaria during the Middle Ages. It fell into decay in 907 after a series of defeats by the Magyars. It was secularized in 921 by Duke Arnulf and reestablished in 979 by Emperor Otto II and Duke Otto I of Bavaria. The emperor appointed a new abbot and granted the right of free election of the abbot, freedom from taxes and imperial protection. Thus removed from the suzerainty of the Bavarian rulers, the abbey recovered its prosperity and grew culturally and artistically. Workshops were founded for book and glass painting and for goldsmithing. Around 1030 Ruodlieb, an early German romance of knightly adventure written in Latin verse, was almost certainly written there. In 1165 Holy Roman Emperor Friedrich I visited the abbey.
Because of its naturally protected position, Tegernsee suffered less from war and hardship than other parts of Bavaria. However, it was infested by the Black Death during the Thirty Years' War. The town experienced tribulations during the War of the Austrian Succession and suffered many casualties in the period from the Austro-Prussian War in 1866 until the end of World
