The Falaise pocket or battle of the Falaise pocket (German: Kessel von Falaise; 12–21 August 1944) was the decisive engagement of the Battle of Normandy in the Second World War. Allied forces formed a pocket around Falaise, Calvados, in which German Army Group B, consisting of the 7th Army and the Fifth Panzer Army (formerly Panzergruppe West), were encircled by the Western Allies. The battle resulted in the destruction of most of Army Group B west of the Seine, which opened the way to Paris and the Franco-German border.

Six weeks after the 6 June 1944 Allied invasion of Normandy, German forces were in turmoil, having expended irreplaceable resources defending the frontline and with Allied air superiority threatening the availability of food and ammunition. However, on the Allied side, British forces had expected to liberate Caen immediately after the invasion, an operation which ended up taking nearly two months, and US forces had expected to control Saint-Lô by the 7 June, yet German resistance delayed this until after Caen's liberation.

The Allied armies developed a multi-stage operation, beginning with Operation Goodwood on 18 July, and continuing with Operation Cobra on 25 July, which saw American forces pushing into a gap around Saint-Lô and overwhelming the defending German forces. On 1 August, Lieutenant General George S. Patton was named the commanding officer of the newly recommissioned US Third Army, which included large segments of the force that had broken through the German lines. The Third Army quickly pushed south and then east, meeting little resistance. Concurrently, the British/Canadian troops pushed south in Operation Bluecoat, attempting to keep the German armour engaged. Four depleted panzer divisions were insufficient to defeat the First US Army, driving the Germans deeper into the Allied envelopment.

On 8 August, Allied ground forces commander General Bernard Montgomery ordered the Allied armies to converge on the Falaise–Chambois area to envelop Army Group B, with the First US Army forming the southern arm, the British the base, and the Canadians the northern arm of the encirclement. The Germans began to withdraw on 17 August, and on 19 August the Allies linked up in Chambois. German counter-attacks forced gaps in the Allied lines, the most significant of which was a corridor forced past the 1st Polish Armoured Division on Hill 262, a commanding position at the pocket mouth. By the evening of 21 August, the pocket had been sealed, with an estimated 50,000 Germans trapped inside. Approximately 20–50,000 German troops managed to escape the pocket before it was closed. The Allied Liberation of Paris came a few days later, and on 30 August the remnants of Army Group B retreated across the Seine, completing Operation Overlord.

Early Allied objectives in the wake of the D-Day invasion of German-occupied France included the deep water port of Cherbourg and the area surrounding the town of Caen. Allied attacks to expand the bridgehead had rapidly defeated the initial German attempts to destroy the invasion force, but bad weather in the English Channel delayed the Allied build-up of supplies and reinforcements, while enabling the Germans to move troops and supplies with less interference from the Allied air forces. Cherbourg was not captured by the VII US Corps until 27 June, and the German defence of Caen lasted until 20 July, when the southern districts were taken by the British/Canadians in Operation Goodwood and Operation Atlantic.

General Bernard Montgomery, the Allied ground forces commander, had planned a strategy of attracting German forces to the east end of the bridgehead against the British/Canadians, while the US First Army advanced down the west side of the Cotentin Peninsula to Avranches. On 25 July the US First Army commander, Lieutenant-General Omar Bradley, began Operation Cobra. The US First Army broke through the German defences near Saint-Lô and by the end of the third day had advanced 15 mi (24 km) south of its start line at several points. Avranches was captured on 30 July and within 24 hours the US VIII Corps of the US Third Army crossed the bridge at Pontaubault into Brittany and continued south and west through open country, almost without opposition.

The US advance was swift and by 8 August, Le Mans, the former headquarters of the German 7th Army, had been captured. After Operation Cobra, Operation Bluecoat and Operation Spring, the German army in Normandy was so reduced that "only a few SS fanatics still entertained hopes of avoiding defeat". On the Eastern Front, Operation Bagration had begun against Army Group Centre which left no possibility of reinforcement of the Western Front. Adolf Hitler sent a directive to Field Marshal Günther von Kluge, the replacement commander of Army Group B after the sacking of Gerd von Rundstedt, ordering "an immediate counter-attack between Mortain and Avranches" to "annihilate" the enemy and make contact with the west coast of the Cotentin peninsula.

Eight of the nine Panzer divisions in Normandy were to be used in the attack, but only four could be made ready in time. The German commanders protested that their forces were incapable of an offensive, but the warnings were ignored and Operation Lüttich commenced on 7 August around Mortain. The first attacks were made by the 2nd Panzer Division, SS Division Leibstandarte and the SS Division Das Reich, but they had only 75 Panzer IVs, 70 Panthers and 32 self-propelled guns. The Allies were forewarned by Ultra signals intercepts, and although the offensive continued until 13 August, the threat of Operation Lüttich had been ended within 24 hours. Operation Lüttich had led to the most powerful remaining German units being defeated at the west side of the Cotentin Peninsula by the US First Army, and the Normandy front on the verge of collapse. Bradley said,