Guy (Italian: Guido) (b.c.1012) is the duke of Sorrento from 1035, the brother of Guaimar IV of Salerno, father-in-law of William Iron Arm and William of the Principate, and brother-in-law of Humphrey of Hauteville.

He is the son of Guaimar III and Gaitelgrima.

Guy's place in history is secured primarily through his relations (by blood and marriage), though his own actions are not inconsequential.

According to John Julius Norwich, he was a "selfless" prince, exhibiting a "moral sense rare for [his] time and position."