The document that formally ended World War I is the Treaty of Versailles, signed on June 28, 1919. Negotiated at the Paris Peace Conference, the treaty imposed heavy reparations and territorial losses on Germany, which made it a vital but contentious agreement. Besides addressing territorial changes, the treaty established the League of Nations, aiming to prevent future conflicts through international cooperation. The harsh terms led to significant political and economic instability in Germany, contributing to the rise of nationalism and eventually World War II. Thus, the Treaty of Versailles not only concluded WWI but also set the stage for future global tensions.