Leopold III (born November 1, 1351 in Vienna; died July 9, 1386 in Sempach) from the Habsburg family was a Duke of Austria, Styria and Carinthia. He was a son of Duke Albert II, and brother of the Dukes Rudolf IV the Founder and Albert III. He frist was the administrator of Tyrol, and was jointly charged with the rule of the Habsburg lands with Albert after Rudolf's death. However, in the Treaty of Neuberg of September 9, 1379, he became the exclusive ruler of Styria (including Wiener Neustadt), Carinthia, Carniola, the Windish March, Gorizia, the Habsburgs' posessions in Friuli, Tirol and Further Austria. In 1368, he acquired Freiburg im Breisgau, in 1375 Feldkirch and in 1382 Trieste. However, his attempts to expand his position in Switzerland and Swabia failed, when he died in the Battle of Sempach.

He was succeeded by his son William. Other sons included Leopold, Frederick, and Ernest the Iron