Sant'Ambrogio sul Garigliano is a comune (municipality) in the Province of Frosinone in the Italian region Lazio, located about southeast of Rome and about southeast of Frosinone.
Sant'Ambrogio sul Garigliano borders the following municipalities: Rocca d'Evandro, Sant'Andrea del Garigliano, Sant'Apollinare. During World War II, due to its position across the Gustav Line, it was mostly destroyed.