Frederick I, Duke of Swabia

Frederick I (c. 1050–1105) was the first Duke of Swabia from the House of Hohenstaufen, from 1079 to 1105. The son of Count Frederick of Büren, he built Hohenstaufen Castle and founded Lorch Abbey.

During the Investiture Controversy he backed King Henry IV against the anti-king Rudolf; in 1079 Henry enfeoffed him with the duchy and betrothed him to his daughter Agnes. Rival claimants confined his rule to northern Swabia until a 1098 settlement recognized Berthold of Zähringen.

In his last years Frederick expanded northwards as protector of Weissenburg Abbey and the bishopric of Speyer. By Agnes he fathered Duke Frederick II and King Conrad III.