Trevi is an ancient town and comune in Umbria, Italy, on the lower flank of Monte Serano overlooking the wide plain of the Clitunno river system. It is 10 km SSE of Foligno and 20 km north of Spoleto.
The population of the comune was c. 8,000 in 2004, with the town proper accounting for about half of that; the rest lives in the frazioni of Borgo, Bovara, Cannaiola, Coste, Pigge, Manciano, Matigge, Parrano, Picciche, San Lorenzo and Santa Maria in Valle. The historical subdivisions of Trevi proper are the terzieri of Castello, Matiggia e Piano; they come into play only for the Palio.
Most of the town, densely inhabited and of decidedly medieval aspect, lies on sharply sloping terrain, only the very center being more or less flat.