William de Berkeley, 1st Marquess of Berkeley

William de Berkeley, 1st Marquess of Berkeley (1426 – 14 February 1492) was an English peer, given the epithet "The Waste-All" by the family biographer and steward John Smyth of Nibley. He was buried at "St. Augustine's Friars, London" according to one source, but most likely in the Berkeley family foundation of St Augustine's Abbey, Bristol.

Descent and Marriages William of Berkley was born to James Berkeley, 1st Baron Berkeley, and Lady Isabel Mowbray at Berkeley Castle in Berkeley, Gloucestershire, in 1426. His first marriage was in 1466 to Elizabeth West, daughter of Reginald West, 6th Baron De La Warr, but he obtained a divorce on 20 November 1467. In November 1468, he married Joan Strangeways, daughter of Sir Thomas Strangeways and Lady Katherine Neville. After the death of his second wife, he married Anne Fiennes, sister of Thomas Fiennes, 8th Baron Dacre, in .

He was invested as a Knight Bachelor on 18 April 1475.

William was created Viscount Berkeley on 21 April 1481, as a Privy Counsellor (PC) on 5 March 1482/83, and as Earl of Nottingham on 28 June 1483.

In order to achieve this, the castle, lands and lordships composing the Barony of Berkeley he settled on King Henry VII and his heirs male, failing which to descend to his own rightful heirs. Thus, in 1553 on the death of King Edward VI, the unmarried grandson of Henry VII, the Berkeley inheritance returned to the family. Therefore, on the death of the 1st Marquis, only the de jure barony title was passed on to his younger brother Maurice, that is to say, he was Baron Berkeley by right, if not actually in possession of the baronial property. The 4th, 5th and 6th barons were also de jure only, with Henry (d. 1613) becoming de facto 7th Baron in 1553.

Accomplishments On 20 March 1469/70, he was challenged by Thomas Talbot, 2nd Viscount Lisle, to settle the claims to his great-uncle Thomas's estates by combat. Thomas was killed in the combat. The battle, known as the Battle of Nibley Green, is notable for being the last battle fought in England entirely between the private armies of feudal magnates.