William Herbert, 1st Baron Powis KB (c. 1573[1] – 7 March 1655[2]) was a Welsh politician who sat in the House of Commons at various times between 1597 and 1629.

[3] His maternal grandfather was Sir Thomas Stanley, who served as Under-Treasurer of the Royal Mint at the Tower of London during the reign of Queen Elizabeth I.

[1] Before 1600, Lord Powis married Lady Eleanor Percy (1583–1650), third daughter of Henry Percy, 8th Earl of Northumberland and his wife, Katherine Neville (eldest daughter and co-heiress of John Nevill, 4th Baron Latymer).

Herbert was buried at St. Mary's Church in Hendon, Middlesex, London.

Through his daughter Katherine's second marriage, she was the mother of Roger Palmer, 1st Earl of Castlemaine, best known for his marriage to Barbara Villiers, one of Charles II's mistresses whom the King ennobled as the Duchess of Cleveland.