Colonel General Sydnam Poyntz, also Sydenham Poynts, (bap. 3 November 1607) was an English soldier who served in the Thirty Years' War and the English Civil War.

After continental military service, he returned to England in 1644 and became an officer in the Parliamentary army. He became commander-in-chief of Parliament's Northern Association and governor of York. He commanded the victorious Parliamentary force in the battle of Rowton Heath on 24 September 1645. The Presbyterians Parliamentary party thought him to be likely to oppose the New Model Army, but in 1647 he was sent by his soldiers a prisoner to Thomas Fairfax. He fought for London against the New Model Army in 1647, and on the collapse of his cause he fled to Holland. He accompanied Lord Willoughby to the West Indies in 1650, and probably settled in Virginia.

Poyntz was the fourth son of John Poyntz of Reigate, Surrey, and Anne Skinner. He was baptised on 3 November 1607. Poyntz was originally apprenticed to a London tradesman, but, being ill-treated by his master, he took service as a mercenary soldier in Holland, and in the Thirty Years' War.

Poyntz wrote a memoir called Relation on his military service abroad between 1625 and 1636, and it gives some idea of what he did although D.N. Farr his biographer in the Oxford Dictionary of National Biography warns that it is "fitfully accurate". and relates that he:

claimed to have served first in English regiments in the Netherlands, entering Lord Vaux's regiment as a private soldier under a Captain Reysby, and soon after that the earl of Essex's regiment under Captain William Baillie. He went on to join the army of Count Mansfeld in Germany and Hungary, and it was following the break up of the army that, he later claimed, he became a prisoner of the Turks.

In 1631 Poyntz fought for John George of Saxony at the Battle of Breitenfeld. He changed sides and fought as a captain in Wallenstein's army in the service of Emperor Ferdinand II at the Battle of Lützen in 1632. He remained in the Imperial army and the following year he campaigned in Silesia and was present at the Battle of Nordlingen in 1634. He left the army and Germany after the Peace of Prague in 1636. His time in Germany was lucrative and he bought an estate probably in the vicinity of Schorndorf. He returned to England that year and wrote his Relation, but when he failed to find employment as a soldier in England, it is likely that he returned to the continent to find further employment in the Thirty Years' War. He may have risen to the rank of sergeant-major, and may have been knighted on the battle-field.

Poyntz returned to England no later than 1644, and on 27 May 1645 was ordered by the House of Commons to have the command of a regiment of horse and a regiment of foot in the army raised by the seven associated northern counties. He was also appointed commander-in-chief of the forces of the northern association, with the title of colonel-general, and, on 19 August, governor of York. On taking command, Poyntz found his troops mutinous for want of pay, and at the siege of Skipton was more in danger from his own men than from the enemy. He was ordered after Battle of Naseby (14 June 1645) to follow the movements of King Charles I, and succeeded in forcing him to an engagement at Rowton Heath, near Chester, on 24 September. Charles lost about eight hundred men killed and wounded and fifteen hundred prisoners. The House of Commons voted Poyntz a reward of £500. He next captured Shelford House and Wiverton Hall in Nottinghamshire, and then laid siege to Newark. He was still besieging Newark when Charles I took refuge in the camp of the Scottish army there, of which Poyntz at once informed the Speaker William Lenthall. At the request of Charles I the commander of the Newark garrison Lord Belasyse agreed terms and surrendered Newark on 8 May to Poyntz.

In February 1646 Poyntz published a vindication of himself, in which he included an account of his earlier life as well as of his recent services (The Vindication of Colonel-General Poyntz against the false and malicious slanders secretly cast forth against him, 1645–1646, 4to). Parliament, however, was so satisfied with his conduct that he was voted £300 a year, and it was decided that his regiment of horse should be one of four to be retained at the general disbanding of the army. The Presbyterian leaders relied upon Poyntz and his troops to oppose the Independents of the New Model Army, but the soldiers of the northern association entered into communication with those of Lord General Thomas Fairfax's New Model Army, and, in spite of the orders of their commander, held meetings and elected agitators. Poyntz was seized by the agitators on 8 July 1647 and sent as a prisoner to Fairfax's headquarters, charged with endeavouring to embroil the kingdom in a new war. He was released by Fairfax on parole; but the latter, who now became commander-in-chief of all the land forces in the service of Parliament, appointed Colonel John Lambert to take command in the north.