George III, Landgrave of Leuchtenberg (13 December 1502 – 21 May 1555) was Landgrave of Leuchtenberg from 1531 to 1555.
George succeeded John IV as Landgrave.
After completing his studies, he became and advisor and treasurer to Emperor Charles V and fought in the Battle of Pavia. His post required that he provide horses and knights to Duke Louis X of Bavaria and to the Emperor to fight the war against the Ottoman Empire. He borrowed the knights and horses, as well as 14000guilders from Elector Palatine Otto Henry.
In 1546, George III and Elector Palatine Frederick III signed the Treaty of Heidelberg, which defined the boundary between Leuchtenberg and the Palatinate and the privileges of Leuchtenberg. George's brother, Christopher of Leuchtenberg (d. 1554) commanded the cavalry in the army of Albert II Alcibiades. Christopher and Albert took several loans from George and the latter was cited before the Reichskammergericht for breach of the peace. He had to temporarily hand over the Lordship of Grünsfeld and compensate the victims of the looting and pillaging. His brother Christopher died impoverished in a guest house in Regensburg. His second brother Hans was mentally ill and lived most of his life with their sister in Wallerstein.