William de Grey, 1st Baron Walsingham PC KC (7 July 1719 – 9 May 1781), was a British lawyer, judge and politician. He served as Lord Chief Justice of the Common Pleas between 1771 and 1780. de Grey was the third son of Thomas de Grey, MP, of Merton, Norfolk, and Elizabeth Windham, daughter of William Windham. He was the younger brother of another Thomas de Grey. The de Grey family had been settled in Norfolk since the 14th century. He was educated at Trinity Hall, Cambridge, was called to the Bar, Middle Temple, in 1742, and became a King's Counsel in 1758. Between 1761 and 1763 he was Solicitor General to Queen Charlotte.