William Richard George Stanley, 9th Earl of Derby (c. 1655 – 5 November 1702), styled Lord Strange from 1655 to 1672, was an English peer and politician.
Derby was the eldest son of Charles Stanley, 8th Earl of Derby, and Dorotha Helena Kirkhoven.
He succeeded his father in the earldom in 1672 and later served as Lord Lieutenant of Lancashire from 1676 to 1687 and again from 1688 to 1701 and of Cheshire from 1676 to 1687. In 1685, Derby petitioned the House of Lords for the restoration of some of the family estates that had been confiscated from his father, including the manors of Hawarden, Bidston, and Broughton, Lancashire.
Following the Glorious Revolution in which King William III supplanted James II, Derby was ordered as Lord Lieutenant of Lancashire to call out the Lancashire Militia in 1689. He raised three regiments of foot and three troops of horse, and was appointed Colonel of the first regiment. However, his younger brother, James, a professional soldier, actually commanded the Lancashire Brigade during the campaign in Ireland.
Lord Derby married Lady Elizabeth Butler, daughter of Thomas Butler, Earl of Ossory, in 1673. His only son James Stanley, Lord Strange, predeceased him.
On his death on 5 November 1702, his junior title of Baron Strange fell into abeyance between his two daughters (it was later called out abeyance in favour of the eldest daughter, Henrietta). He was succeeded in the earldom by his younger brother James Stanley, 10th Earl of Derby. Lady Derby died on 5 July 1717.