The FL1 (until 2012 FR1) is a regional rail route forming part of the Lazio regional railways network (Italian: ferrovie regionali del Lazio), which is operated by Trenitalia, and converges on the city of Rome, Italy.

The electronic destination boards at stations show only the designation "R" (Regional train).

The FL1, a cross-city route, runs from Orte, in the province of Viterbo, in a southerly direction over the Florence–Rome railway as far as Roma Tiburtina.

It then continues, via the Pisa–Livorno–Rome railway east and south of Rome's city centre, to Roma Trastevere.

On 7 December 2006, the new Fiera di Roma railway station was opened to the public, and included in the FL1 route.