James Fiennes, 1st Baron Saye and Sele (c. 1395 – 4 July 1450) was an English soldier and politician, son of Sir William Fiennes (Herstmonceux, Sussex, 1 August 1357 – 18 January 1401/1402) and wife Elizabeth Batisford (- bef. 1407).
Fiennes fought in the Hundred Years' War and served as High Sheriff of Kent in 1436 and High Sheriff of Surrey and Sussex in 1438. He was Constable of Dover and Warden of the Cinque Ports from 1447 to 1450, and Lord High Treasurer of England from 1449 to 1450.
He was summoned to Parliament from 1446 to 1449 and is said to have been created Baron Saye and Sele by letters patent in 1447. Saye and Sele was a supporter of William de la Pole, 1st Duke of Suffolk, the principal power behind the throne of Henry VI.
After Suffolk's deposition and murder in 1450 he was imprisoned in the Tower and beheaded by a mob of the rebels in London under Jack Cade at the Standard in Cheapside on 4 July 1450. He was succeeded in the barony by his son William.