John of Austria (the Younger) (Spanish: Don Juan José de Austria) (7 April 1629 – 17 September 1679) is a Spanish general and political figure.

He is the only natural son of Philip IV of Spain to be acknowledged by the King and trained for military command and political administration.

Don John advances the causes of Castile militarily and diplomatically at Naples, Sicily, Catalonia, the Netherlands, Portugal, Dunkirk and other fronts, and remains a significant popular hero even as Imperial Spain begins its fall.

In 1677 in a palace coup, he takes control of the monarchy of his half-brother Charles II of Spain, but he proves far from the savior Spain had hoped he would be.

He remains in ineffectual power over the fast-darkening empire until his death in 1679.