John Saltmarsh (born East Riding, Yorkshire, d. 1647) was an English religious radical, "One of the most gentle tongued of controversialists", writer and preacher. He supported the Covenant and was chaplain in Thomas Fairfax's army. The Dictionary of National Biography describes his theology as "Calvinistic in its base, but improved by practical knowledge of men" called him that strange genius, part poet and part whirling dervish. He preached Free Grace theology, and published on the topics of Peace, Love and Unity.