Casamari Abbey is a Cistercian abbey in the Province of Frosinone, Lazio, Italy, about 10 kilometers east-south-east of Veroli.
It marks the site of Cereatae, the birthplace of Caius Marius, afterwards known, as inscriptions attest, as Cereatae Marianae, having been separated perhaps by the triumvirs, from the territory of Arpinum. In the early Imperial times it was an independent community.
The current Abbot of the Abbey of Casamari, as of 2017, is the Right Reverend Abbot Dom Eugenio Romagnuolo, President of the Cistercian Congregation of Casamari.