Karl Friedrich Heinrich Marx (10 March 1796 – 2 October 1877) was a German physician and college lecturer.

He had contacts with Jean Paul and attended inter alia lectures by Georg Wilhelm Friedrich Hegel, becoming a follower of his.

For his work on the subject, Die Struktur und das Leben der Venen he was awarded a prize by the university.

In 1819, Sand murdered the poet, August von Kotzebue, Marx was in Vienna on 19 June 1819 for burschenschaft-related activities and was taken into custody for nine months and then released without charge.

In Göttingen he met Heinrich Heine, his discussions about medicine and his treatise, Goettingen in medicinischer, physischer und historischer Hinsicht[2] are mentioned in his travel journal, Die Harzreise.