Duke of Dorset was a title in the Peerage of Great Britain. It was created in 1720 for the politician Lionel Sackville, 7th Earl of Dorset.
History
The Sackville family descended from Sir Richard Sackville. His only surviving son, Thomas Sackville, was a statesman, poet and dramatist and notably served as Lord High Treasurer between 1599 and 1608. He was raised to the Peerage of England as Baron Buckhurst, of Buckhurst in the County of Sussex, in 1567, and was made Earl of Dorset in 1604, also in the Peerage of England. The titles descended in the direct line until the death of his grandson, the third Earl, in 1624. The late Earl was succeeded by his younger brother, the fourth Earl. He was Lord Chamberlain between 1642 and 1649. He was succeeded by his son, the fifth Earl. He married Lady Frances, daughter of Lionel Cranfield, 1st Earl of Middlesex. He was succeeded by his eldest son, the sixth Earl. He succeeded to the Cranfield estates on the death of his maternal uncle Lionel Cranfield, 3rd Earl of Middlesex. In 1675, two years before he succeeded his father, he was raised to the Peerage of England in his own right as Baron Cranfield, of Cranfield in the County of Dorset, and Earl of Middlesex. He was succeeded by his son, the aforementioned seventh Earl, who was made Duke of Dorset in 1720.