Ferdinand I (10 March 1503 – 25 July 1564) is a Central European monarch from the House of Habsburg.

He is Holy Roman Emperor from 1558, king of Bohemia and Hungary from 1526, king of Croatia, Dalmatia, Slavonia, and formally king of Serbia, Galicia (in Eastern Europe), and Lodomeria, etc.

He rules the Austrian hereditary lands of the Habsburgs most of his public life, at the behest of his elder brother Charles V, Holy Roman Emperor and King of Spain.

Ferdinand is Archduke of Austria from 1521 to 1564.

After the death of his brother–in–law Louis II, Ferdinand rules as King of Bohemia and Hungary (1526–1564).

When Charles retires in 1556, Ferdinand becomes his de facto successor as Holy Roman Emperor, and de jure in 1558, while Spain, the Spanish Empire, Naples, Sicily, Milan, the Netherlands, and Franche-Comté go to Philip, son of Charles.

He is at the forefront in the defense of Central Europe against the Ottoman Empire, whose great push into the area beginsin the 1520s.

This fierce contest occupies Ferdinand's energies for most of his life.

Ferdinand's motto is Fiat justitia et pereat mundus: "Let justice be done, though the world perish".