William de Beauchamp, 1st Baron Bergavenny, KG (c. 1343 – 8 May 1411) was an English peer.

He served under Sir John Chandos during the Hundred Years' War, and was created a Knight of the Garter in 1376.

Sir William Beauchamp served on the royal council of king Richard II as sub-chamberlain or acting chief chamberlain of the household from 1378 to 1380 (in place of the formal chamberlain, Robert de Vere (9th Earl of Oxford), who held it by hereditary right, but was still considered a minor).

[2] Upon the death of his first cousin once removed, John Hastings, 3rd Earl of Pembroke, on 30 December 1389, William inherited the lordship of Abergavenny, including Abergavenny Castle.

[4] He entailed the castle and Honour of Abergavenny on the issue male of his body, with remainder to his brother Thomas Beauchamp, 12th Earl of Warwick and his heirs male; his wife enjoyed it in dower until her death in 1435.