Gavrilo Princip (Serbian Cyrillic: Гаврило Принцип, pronounced [ɡǎʋrilɔ prǐntsip]; 25 July [O.S. 13 July] 1894 – 28 April 1918) was the man who assassinated Archduke Franz Ferdinand of Austria and his wife, Sophie, Duchess of Hohenberg, in Sarajevo on 28 June 1914. Princip and his accomplices were arrested and implicated a number of members of the Serbian military, leading Austria-Hungary to issue a démarche to Serbia known as the July Ultimatum. This set off a chain of events that led to World War I. Princip was a Yugoslav nationalist associated with the movement Mlada Bosna (Young Bosnia) which predominantly consisted of Serbs, but also Bosniaks and Croats. During his trial he stated "I am a Yugoslav nationalist, aiming for the unification of all Yugoslavs, and I do not care what form of state, but it must be free from Austria."

Gavrilo Princip was born in Obljaj, a poor part of Bosnia, which was then in the Austria-Hungary empire. His parents, Petar, a postman, and Marija (née Mićić) had nine children, six of whom died in infancy. His impoverished parents could not provide for him and sent him to live with an older brother in Zagreb, now the capital of Croatia.

World War I (WWI), which was predominantly called the World War or the Great War from its occurrence until 1939 (World War II), and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918. It involved all the world's great powers, which were assembled in two opposing alliances: the Allies (based on the Triple Entente of the United Kingdom, France and Russia) and the Central Powers (originally centred around the Triple Alliance of Germany, Austria-Hungary and Italy; but, as Austria–Hungary had taken the offensive against the agreement, Italy did not enter into the war). These alliances both reorganised (Italy fought for the Allies), and expanded as more nations entered the war. Ultimately more than 70 million military personnel, including 60 million Europeans, were mobilised in one of the largest wars in history. More than 9 million combatants were killed, largely because of enormous increases in lethality of weapons, thanks to new technology, without corresponding improvements in protection or mobility. It was the sixth-deadliest conflict in world history, subsequently paving the way for various political changes such as revolutions in the nations involved.