Robert Sackville, 2nd Earl of Dorset (1561–1609) was an English aristocrat and politician, with humanist and commercial interests.
He was the eldest son of Thomas Sackville, 1st Earl of Dorset, by Cecily, daughter of Sir John Baker. His grandfather, Sir Richard Sackville, invited Roger Ascham to educate Robert with his own son, an incident in 1563 that Ascham introduced into his pedagogic work The Scholemaster (1570) as prompting the book. His tutor Claudius Hollyband dedicated to him the French language manuals The French Schoolemaster (1573) and The Frenche Littelton (1576), which would see a combined total of fifteen editions through the year 1609. He matriculated from Hart Hall, Oxford, 17 December 1576, and graduated B.A. and M.A. on 3 June 1579; it appears from his father's will that he was also at New College.
He was admitted to the Inner Temple in 1580 but not called to the bar, and was elected to the House of Commons in 1585 as member for Sussex, aged 23, by his father's influence. In 1588 he sat for Lewes, but represented the county again in 1592–3, 1597–8, 1601, and 1604–8. He was a prominent member of the Commons, serving as a chairman of several committees. At the same time he engaged in trading ventures, and held a patent for the supply of ordnance.
He succeeded to the earldom of Dorset on the death of his father on 19 April 1608. He inherited from his father manors in Sussex, Essex, Kent, and Middlesex, the principal seats being Knole and Buckhurst. Dorset survived his father less than a year, dying on 27 February 1609 at Dorset House, Fleet Street, London. He was buried in the Sackville Chapel at Withyham, Sussex, and left money for the building and endowment of Sackville College.