Atenulf I (died 2 February 1062) was the Lombard count of Aquino who rose to become Duke of Gaeta in Southern Italy during the chaotic middle of the eleventh century.
Guaimar IV of Salerno, the suzerain of both Aversa and Gaeta, intervened on Asclettin's behalf and he defeated Atenulf in battle and took him prisoner.
[2] At this time, however, Pandulf, the natural ally of Atenulf, was assaulting the lands of the abbey of Monte Cassino with Lando.
In Fall 1058, Atenulf's eldest son, who was betrothed to a daughter of Richard I of Capua, died.
Desiderius of Benevento, the new abbot of Montecassino, convinced Richard to extort only 400 sous from the duke, however.