French army commander during the first part of World War I who, though a capable tactician, proved unable to stop the German advance in northern France and was consequently replaced.

Rising steadily in the French army, Lanrezac had by 1914 become a member of the Conseil Supérieur de la Guerre (Supreme War Council) and commander of the 5th Army. Poised on the left flank of the French force that was expected to sweep eastward into Germany through Alsace and Lorraine at the outbreak of World War I, he was compelled to swing his army northward to face the German armies advancing through Belgium. Forced to retreat south under pressure from Gen. Karl von Bülow's German 2nd Army, he became increasingly pessimistic about the outcome of the campaign. On orders of the French commander in chief, Gen. Joseph Joffre, he nevertheless supported the British expeditionary force east of Paris, winning a brilliant tactical victory at Guise (Aug. 29, 1914). His continued retreat, however, led Joffre to replace him on September 3.