He was the oldest son and heir of King John of Bohemia, who died at the Battle of Crécy on 26 August 1346. Charles inherited the County of Luxembourg from his father and was elected king of the Kingdom of Bohemia. On 2 September 1347, Charles was crowned King of Bohemia.
On 11 July 1346, the prince-electors chose him as King of the Romans (rex Romanorum) in opposition to Emperor Louis IV. Charles was crowned on 26 November 1346 in Bonn. After his opponent died, he was re-elected in 1349 and crowned King of the Romans. In 1355 he was crowned King of Italy and Holy Roman Emperor. With his coronation as King of Burgundy in 1365, he became the personal ruler of all the kingdoms of the Holy Roman Empire.