Rudolf III (c. 1378 – 11 June 1419), a member of the House of Ascania, was Duke of Saxe-Wittenberg and Elector of Saxony from 1388 until his death.

He was probably born at the Saxon Wittenberg residence, the eldest son of Duke Wenceslaus I of Saxe-Wittenberg and his wife Cecilia, daughter of Francesco I da Carrara, Lord of Padua.

In 1419, Emperor Sigismund sent him to Bohemia, in order to quash the Hussite uprising that had begun with the Defenestration of Prague.

His coffin was moved to the crypt of the Wittenberg All Saints' Church in the 19th century, and to the family grave during the Second World War.

As he had outlived his male heirs, he was succeeded by his younger brother Albert III.