Enzio (ān´tsēō) or Enzo (ān´tsō), c.1220–72, king of Sardinia, illegitimate son of Holy Roman Emperor Frederick II. He married a Sardinian heiress and was made king of Sardinia by his father. In the wars between Frederick and the pope he fought gallantly in Italy. Helping Modena against Bologna, he was defeated and captured (1249) at Fossalta. Until his death he was kept prisoner in Bologna, in the palace that came to bear his name.