The Rapido is a short river (c.40 km) which flows 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 Gari river (erroneously identified as the Rapido) was the site of a bloodily repulsed and ill-conceived assault by the U.S. 36th Infantry Division, led by General Walker from January 20–22, 1944 when the Allies were attempting to establish a bridgehead in the vicinity of the town of Sant' Angelo, to launch attacks on the Gustav Line near Monte Cassino. The assault was opposed by two battalions from the German 15th Panzer Grenadier Division under General-Lieutenant Rudolf Sperl.
Coordinates: 41°26′N 13°50′E / 41.433°N 13.833°E / 41.433; 13.833