Ernest I (died 31 March or 31 May 1015) was the Duke of Swabia (1012–1015).

He was a younger son of Leopold I, the Babenberg Margrave of Austria.

[1] His mother was called Richardis of Sualafeldgau.

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.