William Arthur Henry Cavendish-Bentinck, 7th Duke of Portland, KG (16 March 1893 – 21 March 1977), styled Marquess of Titchfield until 1943, was a British peer and Conservative politician.

Portland was the elder son of William Cavendish-Bentinck, 6th Duke of Portland, and his wife, Winifred Anna (née Dallas-Yorke). He was elected to the House of Commons as Member of Parliament (MP) for Newark in 1922, a seat he held until he succeeded his father in the dukedom in 1943, and served as a Junior Lord of the Treasury under Stanley Baldwin from 1927 to 1929 and under Ramsay MacDonald in 1932. He also held the honorary posts of Lord Lieutenant of Nottinghamshire between 1939 and 1962 and was the second Chancellor of the University of Nottingham between 1954 and 1971. In 1948 he was made a Knight Companion of the Garter. He also held the appointment of the honorary air commodore of No. 616 Squadron RAF.^[1]

Portland married Ivy Gordon-Lennox, daughter of Colonel Lord Algernon Charles Gordon-Lennox and granddaughter of Charles Gordon-Lennox, 6th Duke of Richmond, on 12 August 1915. They had two daughters:^[2]

• Lady (Alexandra Margaret) Anne Cavendish-Bentinck (6 September 1916 – 21 December 2008)
• Lady (Victoria) Margaret Cavendish-Bentinck (9 October 1918 – 29 August 1955)

He died in March 1977, aged 84, and was interred at the traditional burial place of the Dukes of Portland, in the churchyard of St Winifred's Church at Holbeck.

He was succeeded in the dukedom by his third cousin Ferdinand Cavendish-Bentinck. The subsidiary title Baron Bolsover became extinct on the death.

The heir to the Duke's titles was a distant cousin. Rather than allow the entailed estates to pass with the titles, the Duke arranged to break the entails and thus enrich his own daughters while permanently denuding the titles of both wealth and long-standing rootedness in land and country. The family seat of Welbeck Abbey passed to his elder daughter, Lady Anne, who never married; upon her death, it passed to the son of her deceased younger sister, Lady Margaret, who had died in 1955 aged 36. Lady Margaret had been married to Don Gaetano Parente, Principe di Castel Viscardo, Italy. Her son, named William Henry Marcello Parente (born 18 February 1951), inherited the estates and later served as High Sheriff of Nottinghamshire in 2003.^[3] Meanwhile, the 8th Duke of Portland, who had inherited the titles, continued to live very modestly in Nairobi.

Portland was a second cousin of Queen Elizabeth The Queen Mother.

Little is published of his wealth. His probate was sworn in 1977 at £4,391,478 (equivalent to about £29,000,000 in 2021), three times that of his father's assets passing at point of death (in real terms).^[4]