Ernest the Iron-Willed (German: Ernst der Eiserne; 1377 – 10 June 1424), a member of the House of Habsburg, ruled over the Inner Austrian duchies of Styria, Carinthia and Carniola from 1406 until his death.

Shortly after his birth, his father and his uncle Albert III divided the Habsburg lands by the 1379 Treaty of Neuberg: while Albert and his Albertinian descendants would rule over the Duchy of Austria proper, the Leopoldian line received the Inner Austrian states of Styria, Carinthia and Carniola with the remaining March of Istria, as well as Tyrol and the Further Austrian possessions.

When their elder brother William died in 1406, the remaining three sons of Leopold III agreed about the partition of their patrimony: In the separation agreement of 1406, Ernest received Styria, Carinthia and Carniola, and jointly with his elder brother Leopold IV (the current head of the Leopoldian line) held the guardianship over their minor nephew Albert V of Austria, grandson of Duke Albert III.

In 1414, he became the last Duke to be enthroned according to Carantanian traditional rite at the Prince's Stone in Carinthia, and from that time on called himself 'archduke'.

Ernest died at Bruck an der Mur, and was buried in the Cistercian monastery of Rein near Graz.