Thomas Sackville, 1st Earl of Dorset (1536–April 19, 1608) was an English statesman and poet. He was a Member of Parliament and Lord High Treasurer. His house, Knole House, at Knole in Kent, is celebrated.

He was author, with Thomas Norton, of the play Gorboduc (1562).

He was created Baron Buckhurst, of Buckhurst in the County of Sussex, in 1567, and Earl of Dorset in 1604. Dorset quickly became one of the favourites of King James I, and was soon promoted to Lord High Treasurer. However, Dorset's sqaundering of the Royal Treasury was to prove disastrous to the King's already serious financial situation, and he was nicknamed "Lord Fill-Sack" (a pun on Dorset's last name) for the way in which he would unhesitatingly line his pockets. Dorset died in 1608 and the King's next Treasurer, Lord Suffolk, was also to prove disastrous in terms of corruption and waste.

Queen Elizabeth I acquired Bexhill Manor in 1590 and granted it to Thomas.