Henry William Portman was an 18th century housing developer, the ancestor of the Viscounts Portman.
He was the son and heir of Henry William Berkeley Portman, by his wife Anne Fitch. He succeeded his father in the estates of Bryanston and Orchard Portman in 1761, and to the Berkeley estates at Pylle on the death of his aunt Lady Burland. He developed 200 acres (0.81 km2) of meadow in London (between Oxford Street and the present site of Regent's Canal) he had inherited from his Tudor ancestor Sir William Portman, turning it into the Portman Estate. He began issuing its first building leases in 1755, and building began in 1764 with Portman Square, which was to owe its popularity to buildings by Robert Adam and James ‘Athenian’ Stuart. His development work was continued by his son Edward Berkeley Portman.