British journalist and publisher of the Mercurius Britanicus, an anti-Royalist commentary on news and politics and a forerunner of the modern newspaper.

Needham's father, an attendant to an aristocratic woman, died when Marchamont was an infant, and the boy was raised by his mother, an innkeeper, and her second husband. He studied at All Souls College, Oxford, and later, after contemplating the law and the practice of medicine, was an usher in the school of the Merchant Taylors. He settled on journalism as a career and then took up the Parliamentary cause in his first newsletter, issuing a defense, of which he was probably the primary author, against Royalist attacks in the Mercurius Aulicus, the Royalist publication.

Like Capt. Thomas Audley, who was sometimes identified as the editor of Mercurius Britanicus and the author of attacks on King Charles I (1625–49), Needham was arrested for his writing and released, many times—by both the Royalists and the Parliamentarians.

In 1647, two years before Charles I was beheaded, Needham suddenly changed political sides, supporting the Royalists and assailing the Cromwellians. He published Mercurius Pragmaticus, a violently anti-Parliament newsletter. Then in 1650, just as unpredictably, he reversed himself again and sided with the Parliamentarians in attacking the crown. He edited the Mercurius Politicus, which sought to discredit the Royalist cause and to champion that of the Commonwealth. Needham had to flee to Holland in 1660 but was later pardoned and returned to England to practice medicine. Gradually, however, he again took up his role of pamphleteer. As befitted one so mercurial and intense in his various loyalties, he was the subject of numerous satires and caricatures.