The assassination of Archduke Franz Ferdinand of Austria on June 28, 1914, marked the event that triggered World War I. The archduke, heir to the Austro-Hungarian throne, was killed in Sarajevo by Gavrilo Princip, a member of the nationalist group Black Hand. This act ignited existing tensions among European powers, leading Austria-Hungary to declare war on Serbia. The complex web of alliances between nations quickly mobilized into a broader conflict, transforming a regional dispute into a global war. This event is recognized as the catalyst that led to one of the deadliest conflicts in history and ultimately transformed geopolitical landscapes worldwide.