Sir William Brandon (1456 – 22 August 1485) of Soham, Cambridgeshire was Henry Tudor's standard-bearer at the Battle of Bosworth, where he was killed by King Richard III. He was the father of Charles Brandon, 1st Duke of Suffolk.

William was the son of Sir William Brandon of Wangford, Suffolk, and of Soham, Cambridgeshire, Knight Marshal of Marshalsea (1425 – 4 March 1491) and wife (married 1462) Elizabeth Wingfield (died 28 April 1496/1497). He had numerous siblings, including Sir Thomas Brandon, who fought with him at the Battle of Bosworth and later became a leading courtier and Master of the Horse of Henry VII.

In 1478 Sir John Paston wrote that Brandon had been arrested for an attempted rape: "yonge William Brandon is in warde and arestyd ffor thatt he scholde have fforce ravysshyd and swyvyd an olde jentylwoman ..." By that time he was already married to Elizabeth Bruyn, a widow with two sons, and according to Paston there were rumours he would be hanged for his offence. Brandon apparently escaped prosecution however, because a few years later he was one of the key London connections behind the Buckingham Revolt of 1483, along with his brother Thomas and brother-in-law, Wingfield.

Pardoned in March 1484, he boarded a ship at Mersea in November and sailed for France, where he was supposedly joined by his wife, who gave birth to their eldest son in Paris. He joined his brother Thomas in the relief of the Hammes fortress.

At the Battle of Bosworth, William formed part of Henry Tudor's personal entourage, performing the role of royal standard bearer. When Richard III launched his final charge, he personally unhorsed two men we know by name. Brandon and Sir John Cheney, a well-known jousting champion. While Cheyne lived, Brandon became the most notable victim of the charge, killed by Richard while defending the standard. As such he appears in stanzas 155 and 156 in The Ballad of Bosworth:

amongst all other Knights, remember
which were hardy, & therto wight;
Sir william Brandon was one of those,
King Heneryes Standard he kept on height,

& vanted itt with manhood & might
vntill with dints hee was dr(i)uen downe,
& dyed like an ancyent Knight,
with HENERY of England that ware the crowne.

—Bosworth Ffeilde, anonymous author

According to popular myth William and his brother were both knighted by Henry Tudor when he landed at Milford in 1485, however Thomas was only knighted after the Battle of Blackheath in 1497 and William was presumably only called "Sir William" out of courtesy after his death, or out of confusion with his father, the elder Sir William.