John Gerard, (1632–1654) was a Royalist ensign during the English Civil War and was executed for High Treason against the Protectorate for his part in the Gerard's conspiracy.
Gerard was one of three brothers born to Ratcliffe Gerard (died in or before 1670) of Halsall, Lancashire, and his wife, Jennet (born ca. 1588), daughter of Edward Barrett of Pembrokeshire. His father and elder brother, Gilbert both served in the Royalist army during the Civil War.
Gerard served in the King's army as an ensign, and by the early 1650s had entered the shady world or Royalist conspiracies to overthrow the Commonwealth and restore Charles II to the throne.
In November 1653 Gerard appeared as a witness at the trial of Don Pantaleone Sá, a brother of the Portuguese ambassador, for the murder of an Englishman. The night before the murder Gerard had overheard Pantaleone Sá and his friends talking of English affairs in the street and had given them the lie, whereupon they had attacked him, and, though a little man, yet "he threw him off that was upon him, and so was hustling with him a good while", but was rescued by a passer-by, after he had received a stab in the shoulder. Don Pantaleon Sá was affronted by what he perceived to be a slight on his honour and he returned to the location the next day with an armed retinue to seek revenge. He mistook another man for Gerard and killed him. Pantaleone Sá sought sanctuary in the ambassador's residence, but the Lord Chief Justice, Henry Rolle,supported by other expert opinions, decided that exterritoriality coved the ambassador and not members of his household in cases of murder, so Pantaleone Sá was arrested tried and found guilty of murder and sentenced to be hanged.
Early in 1654 Gerard went over to France, where he was presented to Charles II by his cousin, Charles Gerard, Lord Brandon. Soon after his return to England in May 1654 he was arrested, with two others, on a charge of conspiring against the government in what became known as Gerard's conspiracy. It was alleged that in company with a Royalist major, one Henshaw, whom he had met in France, Gerard with 30 other mounted men were to attack the Lord Protector, Oliver Cromwell as he rode to Hampton Court, and, after overwhelming his body guard and killing him, to besiege Whitehall, seize the Tower of London, and proclaim Charles II king.