The Battle of Mulhouse (German: Mülhausen), also called the Battle of Alsace (French: Bataille d'Alsace), which began on 7 August 1914, was the opening attack of the First World War by the French Army against Germany. The battle was part of a French attempt to recover the province of Alsace, which France had ceded to the new German Empire following defeat in the Franco-Prussian War of 1870–1871. The French occupied Mulhouse on 8 August and were then forced out by German counter-attacks on 10 August. The French retired to Belfort, where General Louis Bonneau, the VII Corps commander, was sacked along with the commander of the 8th Cavalry Division. Events further north led to the German XIV and XV corps being moved away from Belfort and a second French offensive by the French VII Corps, reinforced and renamed the French Army of Alsace (General Paul Pau), began on 14 August.

During the Battle of Lorraine, the principal French offensive by the First and Second armies, the Army of Alsace advanced cautiously into the border province of Lorraine (Lothringen). The French reached the area west of Mulhouse by 16 August and fought their way into the city by 19 August. The German survivors were pursued eastwards over the Rhine and the French took 3,000 prisoners. Joffre ordered the offensive to continue but by 23 August, preparations were halted as news of the French defeats in Lorraine and the Ardennes arrived. On 26 August, the French withdrew from Mulhouse to a more defensible line near Altkirch, to provide reinforcements for the French armies closer to Paris. The Army of Alsace was disbanded, the VII Corps was transferred to the Somme area in Picardy and the 8th Cavalry Division was attached to the First Army, to which two more divisions were sent later. The German 7th Army took part in the counter-offensive in Lorraine with the German 6th Army and in early September was transferred to the Aisne.