Jan Pieterszoon Beelthouwer (c.1603—c.1665) was a Dutch Collegiant controversialist of unorthodox beliefs from Enkhuizen.
He propagated Socinian views.
[1] From around 1644 he had public debates with Isaac Montalto, Jacob Judah Leon and Menasseh ben Israel, Sephardic Jews of Amsterdam.
[2] He was regarded as a heretic in Enkhuizen from 1656.
He wrote against the conservative Mennonite apothecary Lambert Bidloo.