Archduke Franz Ferdinand Carl Ludwig Joseph Maria of Austria (18 December 1863 – 28 June 1914) was the heir presumptive to the throne of Austria-Hungary. His assassination in Sarajevo was the most immediate cause of World War I.

Franz Ferdinand was the eldest son of Archduke Karl Ludwig of Austria, the younger brother of Emperor Franz Joseph I of Austria. Following the death of Crown Prince Rudolf in 1889 and the death of Karl Ludwig in 1896, Franz Ferdinand became the heir presumptive to the Austro-Hungarian throne. His courtship of Sophie Chotek, a lady-in-waiting, caused conflict within the imperial household, and their morganatic marriage in 1900 was only allowed after he renounced his descendants' rights to the throne. Franz Ferdinand held significant influence over the military, and in 1913 he was appointed inspector general of the Austro-Hungarian armed forces.

On 28 June 1914, Franz Ferdinand and his wife were assassinated in Sarajevo by the 19-year-old Gavrilo Princip, a member of Young Bosnia. Franz Ferdinand's assassination led to the July Crisis and precipitated Austria-Hungary's declaration of war against Serbia, which in turn triggered a series of events that eventually led – four weeks after his death – to Austria-Hungary's allies and Serbia's allies declaring war on each other, starting World War I.