Clement Walker (died 1651) was an English lawyer, official and politician. As a member of the Long Parliament, he became an outspoken critic of the conduct of its affairs, and allied himself to William Prynne. Author of the History of Independency, which as a project with several editions included also his Anarchia Anglicana, he was a strong opponent of religious factionalism, and was imprisoned in the Tower of London, where he died without being brought to trial. He used the pseudonym Theodorus Verax.
He was born at Cliffe in Dorset, and is said to have been educated at Christ Church, Oxford, but his name does not appear in the matriculation register. In 1611 he became a student of the Middle Temple, being described as son and heir of Thomas Walker, esq., of Westminster. Before the First English Civil War began, Walker was made usher of the exchequer, an office which he held till February 1650.
Walker had an estate at Charterhouse, Somerset, and was reputed to be an enemy to Puritans; but on the outbreak of the war he supported the parliamentary cause, and on 1 April 1643 became a member of the parliamentary committee for Somerset. He was advocate to the court-martial which condemned Robert Yeomans and George Bouchier (Bowyer) for seeking to betray Bristol to Prince Rupert, and was at first a strong supporter of Colonel Nathaniel Fiennes as governor of that city. After the surrender of Bristol by Fiennes to Prince Rupert, Walker became his most bitter enemy, co-operated with William Prynne in publishing pamphlets against him, and finally secured his condemnation by a court-martial. One of these pamphlets was complained of by William Fiennes, 1st Viscount Saye and Sele, father of Colonel Fiennes, to the House of Lords, on the ground that it impugned his reputation. Walker was consequently arrested, brought before the house, fined £100, and ordered to pay £500 damages to Lord Say. He refused to make the submission that was also demanded, alleging that it was against the liberty of the subject, and that, as he was a commoner and a member of a committee appointed by the House of Commons, he ought not to be judged by the lords without being heard also by the lower house. He was sent to the Tower (7 October 1643), but released on bail (3 November) after he had petitioned the commons and caused his articles against Fiennes to be presented to them.