Ernest I (died March 31 or May 31, 1015) was Duke of Swabia (1012–1015). He was a younger son of Leopold I, the Babenberg Margrave of Austria. In 1012 Henry II, King of Germany, gave the Duchy of Swabia to Ernest following the death of its childless ruler Hermann III. In order to further legitimatize his rule as duke, he married Gisela of Swabia, the eldest sister of Hermann. Ernest and Gisela had two sons, Ernest and Hermann, both of whom would eventually become dukes of Swabia themselves. Ernest died in 1015 as a result of a hunting accident and was succeeded by his son Ernest. He was buried in Würzburg.