The significant event that marked the end of hostilities in World War I was the signing of the Armistice on November 11, 1918. This agreement between the Allied Powers and Germany halted the fighting on the Western Front, effectively ceasing military operations. The Armistice led to the eventual signing of the Treaty of Versailles in 1919, which formally concluded the war. It represented a turning point, not just in military terms, but also politically and socially, as nations worked to negotiate peace and address the lasting impacts of the conflict.