San Felice Circeo is about 100 kilometres south of Rome by road — an hour and a half by car on the A1 motorway (Rome direction) and then south via Latina, or via the Via Pontina (SS148). The approach through the Pontine Plain, crossing kilometre after kilometre of flat agricultural land before the Monte Circeo promontory appears suddenly above it, is itself an interesting drive.
By public transport, take a train from Rome Termini to Priverno-Fossanova (on the Rome–Naples line), then a bus toward Sabaudia and San Felice Circeo. Service is infrequent and the connections require planning — check COTRAL timetables in advance. Most visitors with the ability to rent a car should do so.
There is no direct connection from Naples (about 150 kilometres south). Arriving from the south, drive north via Terracina on the Via Appia (SS7), which passes through Terracina and then along the coast.