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. Baron Saye and Sele, the Lord High Treasurer, was brought to Guildhall for a sham trial. Upon being found guilty of treason, he was paraded through part of London and beheaded by a mob of the rebels in London under Jack Cade at the Standard in Cheapside on 4 July 1450. Fiennes' son-in-law William Cromer was also executed by the rebels. The heads of the two men were put on pikes and unceremoniously paraded through the streets of London while their bearers pushed them together so that they appeared to kiss. He was succeeded in the barony by his son William.
He married Emmeline Crowmer (1398 – 5 January 1452), daughter of William Cromer, twice Lord Mayor of London. Their children included:Elizabeth de Fiennes (1348 – 1386), married first her maternal uncle Sir William Cromer (c.1422 – 1450), Lord of Turnstall, then secondly to Alexander Iden, Lord of Westwell, both of whom attained the position of High Sheriff of Kent; and
William de Fiennes, 2nd Baron Saye and Sele (b. circa 1428 at Broughton Castle, Broughton, Bloxham Hundred, Oxfordshire; d. 1471 during the Battle of Barnet, Barnet, then in Hertfordshire).
James appears as a named character in the historical play Henry VI, Part 2, written by the famed English bard, William Shakespeare. His son William was an actual participant in the War of the Roses, and in the decisive Battle of Barnet referenced in the final part of Shakespeare's trilogy, Henry VI, Part 3.