Onorato I Caetani (c. 1336 – 20 April 1400) was an Italian nobleman, who was the count of Fondi from 1348 and the Great Constable of the Kingdom of Naples also from 1348.
In 1367, Pope Urban V excommunicated Caetani, who was besieging Ferentino and was forced to retreat by a papal army.
This period was Caetani's apex: he defeated his rivals at Ninfa, built a fortress at Castellonorato (in the modern comune of Formia, 1380), reclaimed several areas of southern Lazio and distributed lands to his peasants.
Charles, after capturing Naples, executed Baldassarre of Brunswick, Caetani's brother-in-law and his main link with the Neapolitan court, and hired Onorato's brother Giacomo to conquer Fondi.
After losing Anagni, Sezze and Cisterna, he launched a desperate assault on Rome (15 January 1400), but was defeated at Porta del Popolo.