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