29 June] 1844 – 16 August 1921) reigned as the last King of Serbia (1903–1918) and as the first King of the Serbs, Croats and Slovenes (1918–1921).
Since he was the king of Serbia during a period of great Serbian military success, he was remembered by Serbian people as King Peter the Liberator, and also known as Old King.
Peter was Karadorde's grandson and third son of Persida Nenadovic and Prince Alexander Karadordevic, who was forced to abdicate.
Peter lived with his family in exile.
He fought with the French Foreign Legion in the Franco-Prussian War.
He joined as volunteer under the alias Peter Mrkonjic in the Herzegovina Uprising (1875–77) against the Ottoman Empire.
He married Princess Zorka of Montenegro, daughter of King Nicholas, in 1883.
She gave birth to his five children, including Prince Alexander.
After the death of his father in 1885, Peter became head of the Karadordevic dynasty.
After a military coup d'état and the murder of King Alexander I Obrenovic in 1903, Peter became King of Serbia.
As king, he advocated a constitutional setup for the country and was famous for his libertarian politics.
King Peter was the supreme commander of the Serbian army in the Balkan wars.
Because of his age, on 24 June 1914, he proclaimed his son, Alexander, heir-apparent to the throne, as regent.
In the First World War he and his army retreated across the Principality of Albania.