Sir William Portman, 6th Baronet

Sir William Portman, 6th Baronet, FRS (5 September 1643 – 18 March 1690) was an English politician who represented Taunton and Somerset in the House of Commons of England from 1661 to 1690. Portman was the son of Sir William Portman, 5th Baronet and his wife Anne Colles, daughter of John Colles. He inherited the baronetcy on the death of his father in 1646.

In 1661, Portman was elected Member of Parliament for Taunton for the Cavalier Parliament and held the seat until 1679. In 1679 he was elected MP for Somerset where he sat until 1685. He was then elected MP for Taunton again, and held the seat until his death in 1690. Portman married three times but died without issue and the baronetcy became extinct.

He matriculated at All Souls' College, Oxford, 26 April 1659, and at the Restoration of 1660 was made a Knight of the Bath. He represented Taunton in parliament from 1661 until 1679, and from 1685 till his death. From 1679 to 1681 he sat for the county of Somerset. Apart from Sir Edward Seymour, he was accounted as influential a tory as any in the west of England.

He left his valuable estate to his first cousin Henry Seymour , the 5th son of his aunt Anne Portman and her husband Sir Edward Seymour, 3rd Baronet . Henry Seymour assumed the name and arms of Portman, and although twice married, left no male progeny. Under Sir William's will his next heir was another cousin, William Berkeley of Pylle, Somerset, great-grandson of his other aunt, Joan Portman, sister of Anne Portman . Joan had married Sir George Speke of Whitelackington, Somerset, and their daughter Philippa Speke became the wife of Edward Berkeley of Pylle, 4th in descent in a junior line from Richard Berkeley of Stoke Gifford, Gloucestershire, which manor had been granted in 1337 by Maurice de Berkeley, 2nd Baron Berkeley (1271-1326) to his second son Maurice de Berkeley . Philippa's son was Edward Berkeley MP, of Pylle, who married Elizabeth Ryves, daughter of John Ryves of Ranston, Dorset. Their second son was William Berkeley of Pylle (who was heir to his elder brother Maurice Berkeley MP of Pylle) who became in 1728 the second heir of Sir William Portman, 6th Baronet, who like his first heir Henry Seymour, changed his surname to Portman by a private act of Parliament, Portman's Name Act 1735 (9 Geo. 2. c. 22 ). He also assumed the arms of Portman which he quartered with his paternal arms of Berkeley of Stoke Gifford, placing the Portman arms in the 1st and 4th quarters of greatest honour. His grandson Henry William Portman gave his name to Portman Square in London (begun in 1764), and was grandfather of Edward Berkeley Portman, 1st Viscount Portman (1799-1888). Bryanston Square is named after Bryanston, the seat and estate purchased by Sir William in Dorset shortly before his death.