Frederick II, duke of Swabia (born 1090)

Frederick II, called the One-Eyed, was Duke of Swabia from 1105 until his death, the second from the Hohenstaufen dynasty. His younger brother Conrad was elected King of the Romans in 1138.

The Duchy of Swabia was one of the five stem duchies of the medieval German Kingdom. It arose in the 10th century in the southwestern area that had been settled by Alemanni tribes in Late Antiquity.