San Giorgio a Liri is a comune (municipality) in the Province of Frosinone in the Italian region Lazio, located about southeast of Rome and about southeast of Frosinone.
The little town is located in the southernmost part of the province of Frosinone, between the Aurunci mountains and the Liri river. San Giorgio a Liri borders the following municipalities: Castelnuovo Parano, Esperia, Pignataro Interamna, Sant'Apollinare, Vallemaio.