World War I, which lasted from 1914 to 1918, was a global conflict that had a major impact on many aspects of modern life. The main causes of this war were rooted in imperial rivalries, nationalism, and complex military alliances. Understanding these factors is important to see their impact on the world today. One of the main causes was rivalry between the great European powers, including Britain, France, Germany and Russia. This competition was largely fueled by the desire to expand territory and explore new resources. Nationalism, especially in the Balkans, is increasingly heating up tensions. On 28 June 1914, the assassination of Prince Franz Ferdinand in Sarajevo by Gavrilo Princip, a member of the Serbian nationalist group, was the immediate trigger for the conflict. Anyone who witnessed this event would not have thought that a local incident could trigger a major war. Military alliances also play an important role in conflict escalation. The alliance system formed before the war divided Europe into two camps: the Triple Alliance (Britain, France, Russia) and the Central Powers (Germany, Austria-Hungary, Ottomans). When one country gets involved in a conflict, other countries are forced to step in, causing the war to spread across continents and even to different parts of the world. The impacts of World War I were complex and long-term. First, geopolitical shifts occurred, resulting in the collapse of several large empires such as Austria-Hungary, Ottoman, and Russia. New countries emerged, such as Czechoslovakia and Yugoslavia, which now had influence in European political dynamics. The war also triggered significant social change. Women’s participation in the workforce increased drastically as men went to war. This gave rise to women’s suffrage movements in many countries, further strengthening their position in society. Dissatisfaction with political conditions after the war, including the handling of the economy, became the basis for the growth of totalitarianism in Italy, Germany and other countries. Economically, World War I had a profound impact. The extremely high costs of war caused many countries to experience extreme inflation and extraordinary debt. This, in turn, contributed to the Great Depression of the 1930s, which added to global economic chaos. In the contemporary context, many of the problems sparked by World War I are still relevant. State boundaries determined after the war are still a source of conflict today in a number of regions, especially in the Middle East and the Balkans. Additionally, military experiences and strategies used during the war influence modern military doctrine. Signs of violence and extremism, much of which is rooted in post-war discontent, are still visible throughout the 20th century and now. For this reason, studying the history and impact of World War I is very important so that we can understand and draw lessons from past mistakes in order to create a more stable peace in the future.