Sir William de Beaumont, 2nd Viscount Beaumont (April 1438 – 19 December 1507) was a soldier and landowner who was a leading supporter of the Lancastrian faction during the Wars of the Roses.
He was the son of John Beaumont, 1st Viscount Beaumont and Elizabeth, daughter of Sir William Phelip. He was born at Edenham, Lincolnshire. Although his exact date of birth is not recorded, parish records show the date of his baptism as 23 April 1438.
Sir William led an uneventful life until the feud between the houses of York and Lancaster broke into open bloodshed. While he always claimed in life "...to let each man place his feet in the soil as the good lord intended...", he ultimately sided with the Lancastrians.
He fought in several of the major battles of the Wars of the Roses. He was probably knighted before the Battle of Northampton, where his father was killed. He fought at the Battle of Towton, the bloodiest battle ever fought on English soil, but was taken prisoner and attainted along with other prominent Lancastrian lords. Beaumont obtained a general pardon two days before Christmas, but all his lands were declared forfeit and granted to Lord Hastings. This action erected a permanent barrier to any reconciliation with King Edward.
After the restoration of Henry VI in November 1470, King Henry revoked the bill of attainder and restored Sir William's lands and titles. However, the following April, he opposed Edward's landing at Ravenspur. He joined forces with the Duke of Exeter, but they were too weak and were forced to stand aside at Newark and allow Edward to march south to London.
Beaumont fought under Oxford at the Battle of Barnet, but suspecting treachery, they fled. With the Yorkist Edward IV on the throne again, Beaumont was once more stripped of his lands and titles.