William Cavendish-Bentinck, 6th Duke of Portland

His Grace The Duke of Portland KG GCVO TD PC DL
The Duke of Portland, circa 1900.
Master of the Horse
In office 9 August 1886 – 11 August 1892
Monarch	Queen Victoria
Prime Minister	The Marquess of Salisbury
Preceded by	The Earl of Cork
Succeeded by	The Viscount Oxenbridge
In office 16 July 1895 – 4 December 1905
Monarch	Queen Victoria Edward VII
Prime Minister	The Marquess of Salisbury Arthur Balfour
Preceded by	The Earl of Cork
Succeeded by	The Earl of Sefton
Personal details
Born	28 December 1857
Died	26 April 1943(1943-04-26) (aged 85)
Nationality	British
Political party	Conservative
Spouse(s)	Winifred Dallas-Yorke (1863–1954)

William John Arthur Charles James Cavendish-Bentinck, 6th Duke of Portland KG GCVO TD PC DL (28 December 1857 – 26 April 1943), known as William Cavendish-Bentinck until 1879, was a British landowner, courtier and Conservative politician. He notably served as Master of the Horse between 1886 and 1892 and again between 1895 and 1905.

Portland was the son of Lieutenant-General Arthur Cavendish-Bentinck by his first wife Elizabeth Sophia Hawkins-Whitshed, daughter of Sir St Vincent Hawkins-Whitshed, 2nd Baronet and granddaughter of Admiral Sir James Hawkins-Whitshed, 1st Baronet. His paternal grandparents were Lord Charles Bentinck and his second wife Anne Wellesley, the natural daughter of Richard Wellesley, 1st Marquess Wellesley. His great-great-uncle was Arthur Wellesley, 1st Duke of Wellington. Lord Charles was the third son of Prime Minister William Cavendish-Bentinck, 3rd Duke of Portland by his wife Lady Dorothy Cavendish, daughter of William Cavendish, 4th Duke of Devonshire and Lady Charlotte Boyle. Portland's mother died only a few days after his birth. He was educated at Eton. He inherited the Cavendish-Bentinck estates, based around Welbeck Abbey in Nottinghamshire, from his cousin William Cavendish-Scott-Bentinck, 5th Duke of Portland, in 1879. He also succeeded his stepmother as second Baron Bolsover in 1893. His half-sister Lady Ottoline Morrell was a society hostess and patron of the arts associated with the Bloomsbury Group.