The Duchy of Alsace (Latin: Ducatus Alsacensi, Ducatum Elisatium; German: Herzogtum Elsaß) was a large political subdivision of the Frankish Empire during the last century and a half of Merovingian rule.
Gundoin's duchy comprised both sides of the Vosges, the Burgundian Gate, and the Transjura; there were to be continuous early problems retaining the faithfulness of the Sundgau.
Under Gundoin's successors, the famous Etichonids, the counties — Alsace was already generally divided into a Nordgau and Sundgau — were brought under direct ducal control.
From the very beginning, Gundoin had used monasteries and monastic foundation as tools in spreading his authority and in developing his regional economy by employing the industry of monks for secular benefit.
Following the suppression of the Alemanni in 742–746 by Carloman, son of Charles Martel, the duchy of Alsace was dissolved in 742 when a successor for the deceased Duke Liutfrid was not named.
Some have interpreted the tripartite web of support between Alsatian monasteries, the Etichonid dukes and counts, and Theuderic IV as evidence of an attempt to stay outside of Arnulfing (subsequently Carolingian) control.
There is little evidence for an Alsatian dukedom after that, though some have interpreted references to an Uto dux in 999 as implying that the ducatus Elisatium was still not attached to the Duchy of Swabia by then.