The Battle of Monte Cassino (also known as the Battle for Rome and the Battle for Cassino) was a costly series of four assaults by the Allies against the Winter Line in Italy held by Axis forces during the Italian Campaign of World War II. The intention was a breakthrough to Rome.

At the beginning of 1944, the western half of the Winter Line was being anchored by Germans holding the Rapido-Gari, Liri and Garigliano valleys and some of the surrounding peaks and ridges. Together, these features formed the Gustav Line. Monte Cassino, a historic hilltop abbey founded in AD 529 by Benedict of Nursia, dominated the nearby town of Cassino and the entrances to the Liri and Rapido valleys. Lying in a protected historic zone, it had been left unoccupied by the Germans, although they manned some positions set into the steep slopes below the abbey's walls.

Repeated pinpoint artillery attacks on Allied assault troops caused their leaders to conclude the abbey was being used by the Germans as an observation post, at the very least. Fears escalated along with casualties and in spite of a lack of clear evidence, it was marked for destruction. On 15 February American bombers dropped 1,400 tons of high explosives, creating widespread damage. The raid failed to achieve its objective, as German paratroopers then occupied the rubble and established excellent defensive positions amid the ruins.

Between 17 January and 18 May, Monte Cassino and the Gustav defences were assaulted four times by Allied troops. On 16 May, soldiers from the Polish II Corps launched one of the final assaults on the German defensive position as part of a twenty-division assault along a twenty-mile front. On 18 May, a Polish flag followed by the British Union Jack were raised over the ruins. Following this Allied victory, the German Senger Line collapsed on 25 May. The German defenders were finally driven from their positions, but at a high cost. The capture of Monte Cassino resulted in 55,000 Allied casualties, with German losses being far fewer, estimated at around 20,000 killed and wounded.