(1622-1683) Also known as Algernon Sydney. Political writer, son of the 2nd Earl of Leicester, and grand-nephew of Sir Philip Sidney, in his youth travelled on the Continent, served against the Irish Rebels, and on the outbreak of the Civil War, on the side of the Parliament. He was one of the judges on the trial of Charles I., and though he did not attend, he thoroughly approved of the sentence. He opposed the assumption of the supreme power by Cromwell. After the Restoration he lived on the Continent, but receiving a pardon, returned in 1677 to England. He, however, retained the republican principles which he had all his life advocated, fell under the suspicion of the Court, and was in 1683, on the discovery of the Rye House Plot, condemned to death on entirely insufficient evidence, and beheaded on Tower Hill, December 7, 1683. Though no charge of personal venality has been substantiated, yet it appears to be certain that he received money from the French King for using his influence against war between the two countries, his object being to prevent Charles II. from obtaining command of the war supplies. Sidney was deeply versed in political theory, and wrote Discourses concerning Government, puborn in 1698.