Sir John Winter or Wintour (about 1600–1676) was an English ironmaster and landowner at Lydney in Gloucestershire, who was an ardent supporter of Charles I during the English Civil War.
John Winter was the grandson of William Wynter,Vice-Admiral of England, who was granted the manor of Lydney in the Forest of Dean. His parents were Sir Edward Winter and Anne, daughter of the Earl of Worcester.
The Forest of Dean contained rich deposits of iron ore and, with charcoal made from its timber, had been the location of ironworks back to Roman times. Edward Winter had invested in iron making and Sir John continued this family business. There was widespread local opposition to Winter's interference with established commoners' rights in the Forest of Dean. In 1624 it was claimed that Winter "and other Papists" were storing gunpowder and ammunition at his uncle's fortress, Raglan Castle and were plotting rebellion against King James. He obtained a 21-year lease from the Crown for forty thousand cords of wood in 1628, but had to give this up in 1634 when a forest eyre found that he had exceeded his rights. This was the first such court to have been held in the Forest for three hundred years and followed the Skimmington riots of 1631, in which the common people had protested against his enclosures. These riots were part of a general pattern of resistance against enclosure known as the Western Rising.