William Watson-Armstrong, 3rd Baron Armstrong

William Henry Cecil John Robin Watson-Armstrong, 3rd Baron Armstrong (6 March 1919 – 1 October 1987) was an English landowner and peer, a member of the House of Lords from 1972 until his death.

Born at Jesmond Dene House, Newcastle-upon-Tyne, Armstrong was the only son of William Watson-Armstrong, 2nd Baron Armstrong and his wife Zaida Cecile Drummond-Wolff. He was educated at Eton and Trinity College, Cambridge.

On 6 July 1972 he succeeded his father as Baron Armstrong in the peerage of the United Kingdom, an honour recreated for his grandfather in 1903, after he had inherited the Bamburgh Castle and Cragside estates of his cousin, William Armstrong, 1st Baron Armstrong, but not his peerage.

Armstrong decided to live at Bamburgh and gave Cragside, with 911 acres, to the British government in lieu of death duties. In 1977 the house was transferred to the National Trust through the National Land Fund, and Armstrong gave the Trust an endowment.

On 16 August 1947, Armstrong married Baroness Maria-Teresa Chiodelli-Manzoni, a daughter of Italian General Baron Fabrizio Enea Chiodelli-Manzoni. They had no children of their own and adopted a son and daughter.

On Armstrong's death in October 1987, the peerage again became extinct, but the Bamburgh Castle estate passed to his adopted son Francis Watson-Armstrong.