Frederick II of Hohenstaufen (1090 – 1147) was duke of Swabia, succeeding his father, duke Frederick I in 1105. In 1121 he married Judith of Bavaria, a member of the powerful House of Guelph (Welf).

On the death of Emperor Henry V, his uncle, Frederick stood for election as King of Germany with the support of his younger brother Conrad of Swabia and several houses. However, he lost this election of 1125 to Lothar II, crowned Emperor later in 1133.

A conflict erupted between Frederick and his supporters, and Lothar. Encouraged by Albert, Archbishop of Mainz, who loathed the supporters of the late Emperor Henry V, Lothar besieged Nuremberg in 1127. Frederick's second wife, Agnes, was the niece of his old enemy Albert of Mainz.

According to Otto of Freising, Frederick was "so faithful a knight to his sovereign and so helpful a friend to his uncle that by valor he supported the tottering honor of the realm, fighting manfully against its foes..."

Frederick's descendants were:
From Judith of Bavaria (1100-1132)
• Frederick III Barbarrossa (1122-1190), duke of Swabia and Holy Roman Emperor as Frederick I
• Judith of Hohenstaufen (1123-1195), married Matthias I, Duke of Lorraine
From Agnes of Saarbrücken (d.~1147)
• Conrad of Hohenstaufen, Count Palatine of the Rhein (1134-1195)
• Clarissa of Hohenstaufen (1135-1191), married Ludwig II, Duke of Thuringia