John I (died 933 or 934) was the second hypatos of Gaeta of his dynasty, a son of Dociblis I and Matrona, and perhaps the greatest of medieval Gaetan rulers.
He married his daughters off strategically: Gemma to the Sorrentine prefect Marinus; Maru to the Salernitan nobleman Guaifer; and Matrona to Campolo, son of an important Gaetan family.
Together, father and son joined the Byzantine strategos Nicholas Picingli's army marching with its Lombard allies to meet the papal and Spoletan forces.
All together, the Christian league attacked the Moslems of the Garigliano and, in the subsequent battle, the Gaetan hypati distinguished themselves in victory.
He died within the year and left three other sons (Leo, Constantine, and Peter), but Docibilis, who had taken the ducal title in 930, inherited alone and did not divide the realm.