Sidney or Sydney, Algernon,1622–83, English politician; son of Robert Sidney, earl of Leicester. He served in the parliamentary forces during the English civil war and was a member (1652–53) of the council of state of the Commonwealth, but he opposed the dictatorial rule of Oliver Cromwell. Reappointed (1659) to the council of state, he was abroad at the time of the Restoration (1660) and remained there until 1677, when he returned to England to attend to personal affairs. He soon became associated with the opposition to Charles II, joining Lord William RussellRussell, Lord William,
1639–83, English statesman; younger son of the 1st duke of Bedford. He entered Parliament in 1660. Contempt for the dissolute court and fear of Roman Catholicism and of France led him to join the opposition to Charles II.
..... Click the link for more information. and others in negotiations with French agents and in vague plots for an insurrection, perhaps to place the duke of MonmouthMonmouth, James Scott, duke of
, 1649–85, pretender to the English throne; illegitimate son of Charles II of England by Lucy Walter. After his mother's death, he was cared for by Lord Crofts, by whose name the boy was known. In 1662, James went to live at Charles's court.
..... Click the link for more information. on the throne. His implication in these conspiracies was discovered by the exposure of the Rye House PlotRye House Plot,
1683, conspiracy to assassinate Charles II of England and his brother James, duke of York (later James II), as they passed by Rumbold's Rye House in Hertfordshire on the road from Newmarket to London.
..... Click the link for more information. . After a brutal and arbitrary trial by Judge Jeffreys, Sidney was convicted of treason and executed. Sidney's liberal ideals were set forth in his Discourses Concerning Government (1698), a treatise that had great influence on 18th-century political thought, especially in the American colonies.
See biography by A. C. Ewald (2 vol., 1873); J. Scott, Algernon Sidney and the English Republic 1623–1677 (1988).