Karl Theodor, Duke in Bavaria (9 August 1839 – 30 November 1909), was a member of the House of Wittelsbach and a professional oculist.

When he left active duty, he became a student at the Ludwig Maximilian University of Munich, where he studied philosophy, law, economics, and medicine.

In 1870, Karl Theodor's studies were interrupted by the Franco-Prussian War in which he served as a proprietary colonel of the 3rd Bavarian Light Horse.

In 1877, Karl Theodor began practicing medicine in Mentone on the Côte d'Azur, often assisted by his wife Maria Josepha.

They had one child: On 29 April 1874, at Kleinheubach, Karl Theodor married Infanta Maria Josepha of Portugal (1857–1943), daughter of the exiled King Miguel I of Portugal and Princess Adelaide of Löwenstein-Wertheim-Rosenberg, and had five children: Prince Karl Theodor died from kidney trouble at Bayreuth on 30 November 1909.