The Rapido is a short river (c.40 km) which flows through the Ciociaria in the Italian province of Frosinone.

Its source is close to border between Lazio and Molise on the slopes of the Mainarde mountains. The river bathes the district of Sant'Elia Fiumerapido after which it becomes known as the Gari and near Cassino it joins with the Liri to form the Garigliano.

Fed by numerous karstic springs, the river has a relatively high and reliable discharge: 25 m³/s on average and never dropping below 10 m³/s.

The river was the site of a bloodily repulsed assault by the U.S. 36th Infantry Division in January 1944 when the Allies were attempting to establish a bridgehead to launch attacks on the Gustav Line near Monte Cassino.

fr:Rapido (fleuve) it:Rapido (fiume) hu:Gari ja:????? no:Rapido nn:Rapido pl:Rapido (rzeka)