Sir Thomas Fairfax (c. 1475 – 1520) was an owner of Gilling Castle, near Gilling East, North Riding of Yorkshire, England. He and his wife Anne Gascoigne are common ancestors of the Duke and Duchess of Cambridge.
Fairfax's father, also named Thomas, was presumably a supporter of the House of York in the Wars of the Roses. His original home was near the site of the Battle of Towton. Based on the 1349 marriage between Margaret de Etton and their ancestor, a third Thomas Fairfax of Walton, the elder Thomas Fairfax successfully claimed the ownership of the Gilling Estate during two inquisitions, the first of which was in 1489.
The elder Thomas Fairfax married Elizabeth, daughter of Robert Sherburne of Lancashire. Their son, the younger Thomas Fairfax, was the eldest of nine children; his brothers' names were Richard, Robert and John, and his sisters were Jane, Elizabeth, Isabel, Anne and Dorothy.
In 1513, the younger Fairfax served with Henry VIII on his expedition to Artois. He was knighted when the city of Tournai (now in Belgium) surrendered to the king. Upon his father's death in 1505, the younger Thomas Fairfax inherited the Gilling estate.
The younger Fairfax's wife was Agnes (or Anne) Gascoigne, daughter of Lady Margaret Percy, the daughter of Henry Percy, 3rd Earl of Northumberland and through him, a descendant of Edward III. Agnes's father was Sir William Gascoigne "the Younger" of York, son of another Sir William Gascoigne.