John IV (died April or August 1012) was the eldest son of John III of Gaeta and Emilia.
John succeeded his father in 1008 or 1009 and ruled for a brief four years.
John married Sichelgaita, daughter of John IV of Naples and sister of Sergius IV.
He left an infant son, John V,[1] under the regency of his mother, Emilia.
His brother Leo fought for the regency and his cousin Leo tried to usurp the throne from the young John V.