Jan Marek Marci FRS, (June 13, 1595, (, ), Royal Bohemia, Bohemian Crownland, AustriaApril 10, 1667, Prague, R.Bohemia, Bohemian Crownland, Austria), or Johannes () Marcus Marci, was a Bohemian doctor and scientist, rector of the University of Prague, and official physician to the Holy Roman Emperors.