Ivan (Janez) Regen (known also as Johann Regen) (December 9, 1868 – July 27, 1947) was a Slovenian biologist, best known for his studies in the field of bioacoustics.
Ivan (Janez) Regen (også kendt som Johann Regen) (9. december 1868 – 27. juli 1947) var en slovensk biolog, der er bedst kendt for sine studier inden for bioakustik.