Presbyterian minister and popular Puritan leader. He was an influential preacher to the English Parliament and a participant in the formulation of his church's creed.

By 1629 Marshall had become a vicar at Finchingfield, Essex, a position he held until 1651, when personal dissatisfaction caused him to move to Ipswich as town preacher. From 1640 he was also lecturer at St. Margaret's, Westminster. The following year he joined in an attack, published under the name Smectymnuus (q.v.), on the policies of church government and liturgy.

In 1643 Marshall became a member of the Westminster Assembly, a body of clerics and laymen convened by Parliament to determine the nature and doctrine of the English church. When in 1646 Parliament ordered that Presbyterianism be established in England, he was nominated to serve as an elder in his local classis, or district ruling body.

Marshall was influential primarily through his sermons. Though he never held an official position in London, his ability as a spokesman enabled him to win support in the House of Commons for liturgical and episcopal reforms. He was also active in the preparation of the Shorter Westminster Catechism (1647), still a major statement of Presbyterian belief.