John V (died 1042/1053) was the son and successor of Sergius IV as Duke of Naples from 1034 until his death.
In the same year, Sergius IV's sister died and her husband, Rainulf Drengot, returned to Pandulf's allegiance.
At this time, Sergius retired to the monastery of the Holy Saviour in insula maris, where the Castello del'Ovo now stands.
He was succeeded by his son John V, who allied with Guaimar IV of Salerno, another enemy of Pandulf's.
John did homage to Guaimar IV -as a vassal- and remained faithful to him throughout his reign.