Johan Isaksson Pontanus (also known as Johan Isaksen Pontanus; 1571–1639) was a Danish royal historiographer. Pontanus, the brother of the painter Pieter Isaacsz, was born in Denmark but grew up in Holland. He visited Denmark a couple of times and became acquainted with Tycho Brahe and Arild Huitfeldt. In 1604 he became professor at the school in Harderwijk and in 1618 was appointed as the Royal Danish official historian, with the task of writing the history of Denmark in Latin. He continued writing this work until his death but only managed to publish the first part of his Historia Rerum Danicarum (1631).