Idiophyseter[1] is a genus of macroraptorial sperm whale from the Miocene.

Its fossils have been found in Templeton California.

[2] Idiophyseter was small in size compared to modern genera and its maxilla has single-rooted alveoli.

It lacked ventral internal process of the sort present in the modern day genus of sperm whale (Physeter).

This prehistoric cetacean-related article is a stub.