Guaimar IV (c. 1013 – ass.

June 2 or 3, 1052) was Prince of Salerno (1027–1052), Duke of Amalfi (1039–1052), Duke of Gaeta (1040–1041), and Prince of Capua (1038–1047) in Southern Italy over the period from 1027 to 1052.

He is an important figure in the final phase of Byzantine authority in the Mezzogiorno and the commencement of Norman power.

He is, according to Amatus of Montecassino, "more courageous than his father, more generous and more courteous; indeed he possessed all the qualities a layman should have—except that he took an excessive delight in women."

(Cestui Gamérie estoit plus vaillant que le père et plus liberal et courtois à donner, liquel estoit aorné de toutes les vertus que home sécular doit avoir fors de tant que moult se délictoit de avoir moult de fames.)