Alexander I (Aleksandar I Karadordevic, , ), also known as Alexander the Unifier (Aleksandar Ujedinitelj, , – 9 October 1934) served as a prince regent of the Kingdom of Serbia from 1914 and later became King of Yugoslavia from 1921 to 1934 (prior to 1929 the Kingdom was known as the Kingdom of Serbs, Croats and Slovenes).